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Acetylene, The Principles Of Its Generation And Use by F. H. Leeds and W. J. Atkinson Butterfield

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bottoms, being thus deprived of their support, drop down. It is possible
in this way to effect the discharge of the several carbide-holders by
gradual turning of the winch _i_.

"The washer B is provided with a thermometer _m_ passing through a
sound stuffing-box and extending into the water.

"The gasholder C is provided with a scale and pointer, which indicate how
much gas there is in it. It is connected with the pressure-gauge
_n_, and is further provided with a control thermometer _o_.
The gas exit-pipe _q_ can be shut off by a cock. There is a cock
between the gasholder and the washer for isolating one from the other.

"The dimensions of the apparatus are such that each carbide-holder can
contain readily about half a kilogramme (say l lb.) of carbide. The
gasholder is of about 200 litres (say 7 cubic feet) capacity; and if the
bell is 850 mm. (= 33-1/2 inches) high, and 550 mm. (= 21-1/2 inches) in
diameter it will admit of the position being read off to within half a
litre (say 0.02 cubic foot)."

The directions of the German Association for sampling a consignment of
carbide packed in drums each containing 100 kilogrammes (say 2 cwt.) have
already been given in the rules of that body. They differ somewhat from
those issued by the British Association (_vide ante_), and have
evidently been compiled with a view to the systematic and rapid sampling
of larger consignments than are commonly dealt with in this country.
Drawing a portion of the whole sample from every tenth drum is
substantially the same as the British Association's regulations for cases
of dispute, viz., to have one unopened drum (_i.e._, one or two
cwt.) per ton of carbide placed at the analyst's disposal for sampling.
Actually the mode of drawing a portion of the whole sample from every
tenth vessel, or lot, where a large number is concerned, is one which
would naturally be adopted by analysts accustomed to sampling any other
products so packed or stored, and there in no reason why it should be
departed from in the case of large consignments of carbide. For lots of
less than ten drums, unless there is reason to suspect want of
uniformity, it should usually suffice to draw the sample from one drum
selected at random by the sampler. The analyst, or person who undertakes
the sampling, must, however, exercise discretion as to the scheme of
sampling to be followed, especially if want of uniformity of the several
lots constituting the consignment in suspected. The size of the lumps
constituting a sample will be referred to later.

The British Association's regulations lead to a sample weighing about 3
lb. being obtained from each drum. If only one drum is sampled, the
quantity taken from each position may be increased with advantage so as
to give a sample weighing about 10 lb., while if a large number of drums
is sampled, the several samples should be well mixed, and the ordinary
method of quartering and re-mixing followed until a representative
portion weighing about 10 lb. remains.

A sample representative of the bulk of the consignment having been
obtained, and hermetically sealed, the procedure of testing by means of
the apparatus already described may be given from the German
Association's directions:

"The first carbide receptacle is filled with 300 to 400 grammes (say 3/4
lb.) of any readily decomposable carbide, and is hung up in the apparatus
in such a position with regard to the slot _e_ on the disc _d_
that it will be the first receptacle to be discharged when the winch
_i_ is turned. The tin or bottle containing the sample for analysis
is then opened and weighed on a balance capable of weighing exactly to
1/2 gramme (say 10 grains). The carbide in it is then distributed
quickly, and as far as may be equally, into the nine remaining carbide
receptacles, which are then shut and hung up quickly in the generator.
The lid _b'_ is then screwed on the generator to close it, and the
empty tin or bottle, from which the sample of carbide has been removed,
is weighed.

"The contents of the first carbide receptacle are then discharged by
turning the winch _i_. Their decomposition ensures on the one hand
that the sealing water and the generating water are saturated with
acetylene, and on the other hand that the dead space in the generator is
brought under the pressure of the seal, so that troublesome corrections
which would otherwise be entailed are avoided. After the carbide is
completely decomposed, but not before two hours at least have elapsed,
the cock _p_ is shut, and the gasholder is run down to the zero mark
by opening the cock _q_. The cock _q_ is then shut, _p_ is
opened, and the analytical examination proper is begun by discharging the
several carbide receptacles by turning the winch _i_. After the
first receptacle has been discharged, five or ten minutes are allowed to
elapse for the main evolution of gas to occur, and the cock _p_ is
then shut. Weights are added to the gasholder until the manometer
_n_ gives the zero reading; the position of the gasholder C is then
read off, and readings of the barometer and of the thermometer _o_
are made. The gasholder is then emptied down to the zero mark by closing
the cock _p_ and opening _q_. When this is done _q_ is
closed and _p_ is opened, and the winch _i_ is turned until the
contents of the next carbide receptacle are discharged. This procedure is
followed until the carbide from the last receptacle has been gasified;
then, after waiting until all the carbide has been decomposed, but in any
case not less than two hours, the position of the gasholder is read, and
readings of the barometer and thermometer are again taken. The total of
the values obtained represents the yield of gas from the sample
examined."

The following example is quoted:

Weight of the tin received, with its contained |
carbide . . . . . ._| = 6325 grammes.
Weight of the empty tin . . . . = 1485 "
_______
Carbide used . . . = 4840 " = 10670 lb.

The carbide in question was distributed among the nine receptacles and
gasified. The readings were:

________________________________________________
| | | | |
| No. | Litres. | Degrees C. | Millimetres. |
|______|__________|______________|_______________|
| | | | |
| 1 | 152.5 | 13 | 762 |
| 2 | 136.6 | " | " |
| 3 | 138.5 | " | " |
| 4 | 161.0 | " | " |
| 5 | 131.0 | " | " |
| 6 | 182.5 | 13.5 | " |
| 7 | 146.0 | " | " |
| 8 | 163.0 | 14.0 | " |
| 9 | 178.5 | " | " |
|______|__________|______________|_______________|

After two hours, the total of the readings was 1395.0 litres at 13.5 deg. C.
and 762 mm., which is equivalent to 1403.7 litres (= 49.57 cubic feet) at
15 deg. C. and 760 mm. (or 60 deg. F. and 30 inches; there is no appreciable
change of volume of a gas when the conditions under which it is measured
are altered from 15 deg. C. and 760 mm. to 60 deg. F. and 30 inches, or
_vice versa_).

The yield of gas from this sample is therefore 1403.7/4.840 = 290 litres
at 15 deg. C. and 760 mm. per kilogramme, or 49.57/10.67 = 4.65 cubic feet at
60 deg. F. and 30 inches per pound of carbide. The apparatus described can,
of course, be used when smaller samples of carbide only are available for
gasification, but the results will be less trustworthy if much smaller
quantities than those named are taken for the test.

Other forms of carbide-to-water apparatus may of course be devised, which
will equally well fulfil the requisite conditions for the test, viz.,
complete decomposition of the whole of the carbide without excessive rise
of temperature, and no loss of gas by solution or otherwise.

An experimental wet gas-motor, of which the water-line has been
accurately set (by means of the Gas Referees' 1/12 cubic foot measure, or
a similar meter-proving apparatus), may be used in place of the graduated
gasholder for measuring the volume of the gas evolved, provided the rate
of flow of the gas does not exceed 1/6 cubic foot, or say 5 litres per
minute. If the generation of gas is irregular, as when an apparatus of
the type described above is used, it is advisable to insert a small
gasholder or large bell-governor between the washer and the meter. The
meter must be provided with a thermometer, according to the indications
of which the observed volumes must be corrected to the corresponding
volume at normal temperature.

If apparatus such as that described above is not available, fairly
trustworthy results for practical purposes may be obtained by the
decomposition of smaller samples in the manner described below, provided
these samples are representative of the average composition of the larger
sample or bulk, and a number of tests are made in succession and the
results of individual tests do not differ by more than 10 litres of gas
per kilogramme (or 0.16 cubic foot per pound) of carbide.

It is necessary at the outset to reduce large lumps of carbide in the
sample to small pieces, and this must be done with as little exposure as
possible to the (moist) air. Failing a good pulverising machine of the
coffee-mill or similar type, which does its work quickly, the lumps must
be broken as rapidly as possible in a dry iron mortar, which may with
advantage be fitted with a leather or india-rubber cover, through a hole
in which the pestle passes. As little actual dust as possible should be
made during pulverisation. The decomposition of the carbide is best
effected by dropping it into water and measuring the volume of gas
evolved with the precautions usually practised in gas analysis. An
example of one of the methods of procedure described by the German
Association will show how this test can be satisfactorily carried out:

"A Woulff's bottle, _a_ in the annexed figure, of blown glass and
holding about 1/4 litre is used as the generating vessel. One neck, about
15 mm. in internal diameter, is connected by flexible tubing with a
globular vessel _b_, having two tubulures, and this vessel is
further connected with a conical flask _c_, holding about 100 c.c.
The other neck is provided with tubing _d_, serving to convey the
gas to the inlet-tube, with tap _e_, of the 20-litre measuring
vessel _f_, which is filled with water saturated with acetylene, and
communicates through its lower tubulure with a similar large vessel
_g_. The generating vessel _a_ is charged with about 150 c.c.
of water saturated with acetylene. The vessel _f_ is filled up to
the zero mark by raising the vessel _g_; the tap _e_ is then
shut, and connexion is made with the tube _d_. Fifty grammes (or say
2 oz.) of the pulverised carbide are then weighed into the flask _c_
and this is connected by the flexible tubing with the vessel _b_.
The carbide is then decomposed by bringing it in small portions at a time
into the bulb _b_ by raising the flask _c_, and letting it drop
from _b_ into the generating vessel _a_, after having opened
the cock _e_ and slightly raised the vessel _f_. After the last
of the carbide has been introduced two hours are allowed to elapse, and
the volume of gas in _f_ is then read while the water stands at the
same level in _f_ and _g_, the temperature and pressure being
noted simultaneously."

A second, but less commendable method of decomposing the carbide is by
putting it in a dry two-necked bottle, one neck of which is connected
with _e_, and dropping water very slowly from a tap-funnel, which
enters the other neck, on to the carbide. The generating bottle should be
stood in water, in order to keep it cool, and the water should be dropped
in at the rate of about 50 c.c. in one hour. It will take about three
hours completely to gasify the 50 grammes of carbide under these
conditions. The gas is measured as before.

[Illustration: FIG. 23.--SMALL-SCALE APPARATUS FOR DETERMINING YIELD OF
GAS FROM CARBIDE.]

Cedercreutz has carried out trials to show the difference between the
yields found from large and small carbide taken from the same drum. One
sample consisted of the dust and smalls up to about 3/5 inch in size,
while the other contained large carbide as well as the small. The latter
sample was broken to the same size as the former for the analysis. Tests
were made both with a large testing apparatus, such as that shown in Fig.
22, and with a small laboratory apparatus, such as that shown in Fig. 23.
The dust was screened off for the tests made in the large apparatus. Two
sets of testings were made on different lots of carbide, distinguished
below as "A" and "B," and about 80 grammes wore taken for each
determination in the laboratory apparatus, and 500 grammes in the large
apparatus. The results are stated in litres (at normal temperature and
pressure) per kilogramme of carbide.

___________________________________________________________________
| | | |
| | "A" | "B" |
|_____________________________________________________|______|______|
| | | |
| Lot |Litres|Litres|
| Small carbide, unscreened, in laboratory \ (1) | 276 | 267 |
| apparatus . . . . . / (2) | 273 | 270 |
| Average sample of carbide, unscreened, in \ (1) | 318 | 321 |
| laboratory apparatus . . . / (2) | 320 | 321 |
| Small carbide, dust freed, in large apparatus (1) | 288 | 274 |
| Average sample of carbide, dust freed, in \ (2) | 320 | 322 |
| large apparatus . . . . / | | |
|_____________________________________________________|______|______|

As the result of the foregoing researches Cedercreutz has recommended
that in order to sample the contents of a drum, they should be tipped
out, and about a kilogramme (say 2 to 3 lb.) taken at once from them with
a shovel, put on an iron base and broken with a hammer to pieces of about
2/5 inch, mixed, and the 500 grammes required for the analysis in the
form of testing plant which he employs taken from this sample. Obviously
a larger sample can be taken in the same manner. On the other hand the
British and German Associations' directions for sampling the contents of
a drum, which have already been quoted, differ somewhat from the above,
and must generally be followed in cases of dispute.

Cedercreutz's figures, given in the above table, show that it would be
very unfair to determine the gas-making capacity of a given parcel of
carbide in which the lumps happened to vary considerably in size by
analysing only the smalls, results so obtained being possibly 15 per
cent. too low. This is due to two causes: first, however carefully it be
stored, carbide deteriorates somewhat by the attack of atmospheric
moisture; and since the superficies of a lump (where the attack occurs)
is larger in proportion to the weight of the lump as the lump itself is
smaller, small lumps deteriorate more on keeping than large ones. The
second reason, however, is more important. Not being a pure chemical
substance, the commercial material calcium carbide varies in hardness;
and when it is merely crushed (not reduced altogether to powder) the
softer portions tend to fall into smaller fragments than the hard
portions. As the hard portions are different in composition from the soft
portions, if a parcel is sampled by taking only the smalls, practically
that sample contains an excess of the softer part of the original
material, and as such is not representative. Originally the German
Acetylene Association did not lay down any rules as to the crushing of
samples by the analyst, but subsequently they specified that the material
should be tested in the size (or sizes) in which it was received. The
British Association, on the contrary, requires the sample to be broken in
small pieces. If the original sample is taken in such fashion as to
include large and small lumps as accurately as possible in the same
proportion as that in which they occur in the main parcel, no error will
be introduced if that sample is crushed to a uniform size, and then
subdivided again; but a small deficiency in gas yield will be produced,
which will be in the consumer's favour. It is not altogether easy to see
the advantage of the British idea of crushing the sample over the German
plan of leaving it alone; because the analytical generator will easily
take, or its parts could be modified to take, the largest lumps met with.
If the sample is in very large masses, and is decomposed too quickly,
polymerisation of gas may be set up; but on the other hand, the crushing
and re-sampling will cause wastage, especially in damp weather, or when
the sampling has to be done in inconvenient places. The British
Association requires the test to be made on carbide parcels ranging
between 1 and 2-1/2 inches or larger, because that is the "standard" size
for this country, and because no guarantee is to be had or expected from
the makers as to the gas-producing capacity of smaller material.
Manifestly, if a consumer employs such a form of generator that he is
obliged to use carbide below "standard" size, analyses may be made on his
behalf in the ordinary way; but he will have no redress if the yield of
acetylene is less than the normal. This may appear a defect or grievance;
but since in many ways the use of small carbide (except in portable
lamps) is not advantageous--either technically or pecuniarily--the rule
simply amounts to an additional judicious incentive to the adoption of
apparatus capable of decomposing standard-sized lumps. The German and
Austrian Associations' regulations, however, provide a standard for the
quality of granulated carbide.

It has been pointed out that the German Association's direction that the
water used in the testing should be saturated with acetylene by a
preliminary decomposition of 1/2 kilogramme of carbide is not wholly
adequate, and it has been suggested that the preliminary decomposition
should be carried out twice with charges of carbide, each weighing not
less than 1 per cent. of the weight of water used. A further possible
source of error lies in the fact that the generating water is saturated
at the prevailing temperature of the room, and liberates some of its
dissolved acetylene when the temperature rises during the subsequent
generation of gas. This error, of course, makes the yield from the sample
appear higher than it actually is. Its effects may be compensated by
allowing time for the water in the generator or gasholder to cool to its
original temperature before the final reading is made.

With regard to the measurement of the temperature of the evolved gas in
the bell gasholder, it is usual to assume that the reading of a
thermometer which passes through the crown of the gasholder suffices. If
the thermometer has a very long stem, so that the bulb is at about the
mid-height of the filled bell, this plan is satisfactory, but if an
ordinary thermometer is used, it is better to take, as the average
temperature of the gas in the holder, the mean of the readings of the
thermometer in the crown, and of one dipping into the water of the holder
seal.

The following table gives factors for correcting volumes of gas observed
at any temperature and pressure falling within its range to the normal
temperature (60 deg. F.) and normal barometric height (30 inches). The
normal volume thus found is, as already stated, not appreciably different
from the volume at 15 deg. C. and 760 mm. (the normal conditions adopted
by Continental gas chemists). To use the table, find the observed
temperature and the observed reading of the barometer in the border of
the table, and in the space where these vertical and horizontal columns
meet will be found a number by which the observed volume of gas is to be
multiplied in order to find the corresponding volume under normal
conditions. For intermediate temperatures, &c., the factors may be
readily inferred from the table by inspection. This table must only be
applied when the gas is saturated with aqueous vapour, as is ordinarily
the case, and therefore a drier must not be applied to the gas before
measurement.

Hammerschmidt has calculated a similar table for the correction of
volumes of gas measured at temperatures ranging from 0 deg. to 30 deg. C.,
and under pressures from 660 to 780 mm., to 15 deg. C. and 760 mm. It is
based on the coefficient of expansion of acetylene given in Chapter VI.,
but, as was there pointed out, this coefficient differs by so little from
that of the permanent gases for which the annexed table was compiled, that
no appreciable error results from the use of the latter for acetylene also.
A table similar to the annexed but of more extended range is given in the
"Notification of the Gas Referees," and in the text-book on "Gas
Manufacture" by one of the authors.

The determination of the amounts of other gases in crude or purified
acetylene is for the most part carried out by the methods in vogue for
the analysis of coal-gas and other illuminating gases, or by slight
modifications of them. For an account of these methods the textbook on
"Gas Manufacture" by one of the authors may be consulted. For instance,
two of the three principal impurities in acetylene, viz., ammonia and
sulphuretted hydrogen, may be detected and estimated in that gas in the
same manner as in coal gas. The detection and estimation of phosphine
are, however, analytical operations peculiar to acetylene among common
illuminating gases, and they must therefore be referred to.

_Table to facilitate the Correction of the Volume of Gas at different
Temperatures and under different Atmospheric Pressures._

_____________________________________________________
| | |
| | THERMOMETER. |
| BAR.|_______________________________________________|
| | | | | | | |
| | 46 | 48 | 50 | 52 | 54 | 56 |
| | deg. | deg. | deg. | deg. | deg. | deg. |
|_____|_______|_______|_______|_______|_______|_______|
| | | | | | | |
|28.4 | 0.979 | 0.974 | 0.970 | 0.965 | 0.960 | 0.955 |
|28.5 | 0.983 | 0.978 | 0.973 | 0.968 | 0.964 | 0.959 |
|28.6 | 0.986 | 0.981 | 0.977 | 0.972 | 0.967 | 0.962 |
|28.7 | 0.990 | 0.985 | 0.980 | 0.975 | 0.970 | 0.966 |
|28.8 | 0.993 | 0.988 | 0.984 | 0.979 | 0.974 | 0.969 |
|28.9 | 0.997 | 0.992 | 0.987 | 0.982 | 0.977 | 0.973 |
|29.0 | 1.000 | 0.995 | 0.990 | 0.986 | 0.981 | 0.976 |
|29.1 | 1.004 | 0.999 | 0.994 | 0.989 | 0.984 | 0.979 |
|29.2 | 1.007 | 1.002 | 0.997 | 0.992 | 0.988 | 0.982 |
|29.3 | 1.011 | 1.005 | 1.001 | 0.996 | 0.991 | 0.986 |
|29.4 | 1.014 | 1.009 | 1.004 | 0.999 | 0.995 | 0.990 |
|29.5 | 1.018 | 1.013 | 1.008 | 1.003 | 0.998 | 0.993 |
|29.6 | 1.021 | 1.016 | 1.011 | 1.006 | 1.001 | 0.996 |
|29.7 | 1.025 | 1.019 | 1.015 | 1.010 | 1.005 | 1.000 |
|29.8 | 1.028 | 1.023 | 1.018 | 1.013 | 1.008 | 1.003 |
|29.9 | 1.031 | 1.026 | 1.022 | 1.017 | 1.012 | 1.007 |
|30.0 | 1.035 | 1.030 | 1.025 | 1.020 | 1.015 | 1.010 |
|30.1 | 1.038 | 1.033 | 1.029 | 1.024 | 1.019 | 1.014 |
|30.2 | 1.042 | 1.037 | 1.032 | 1.027 | 1.022 | 1.017 |
|30.3 | 1.045 | 1.040 | 1.036 | 1.030 | 1.025 | 1.020 |
|30.4 | 1.049 | 1.044 | 1.039 | 1.034 | 1.029 | 1.024 |
|30.5 | 1.052 | 1.047 | 1.042 | 1.037 | 1.032 | 1.027 |
|_____|_______|_______|_______|_______|_______|_______|
_____________________________________________________
| | |
| | THERMOMETER. |
| BAR.|_______________________________________________|
| | | | | | | |
| | 58 | 60 | 62 | 64 | 66 | 68 |
| | deg. | deg. | deg. | deg. | deg. | deg. |
|_____|_______|_______|_______|_______|_______|_______|
| | | | | | | |
|28.5 | 0.954 | 0.949 | 0.944 | 0.939 | 0.934 | 0.929 |
|28.6 | 0.958 | 0.953 | 0.947 | 0.943 | 0.938 | 0.932 |
|28.7 | 0.961 | 0.956 | 0.951 | 0.946 | 0.941 | 0.936 |
|28.8 | 0.964 | 0.959 | 0.954 | 0.949 | 0.944 | 0.939 |
|28.9 | 0.968 | 0.963 | 0.958 | 0.953 | 0.948 | 0.942 |
|29.0 | 0.971 | 0.966 | 0.961 | 0.956 | 0.951 | 0.946 |
|29.1 | 0.975 | 0.969 | 0.964 | 0.959 | 0.954 | 0.949 |
|29.2 | 0.978 | 0.973 | 0.968 | 0.963 | 0.958 | 0.952 |
|29.3 | 0.981 | 0.976 | 0.971 | 0.966 | 0.961 | 0.956 |
|29.4 | 0.985 | 0.980 | 0.975 | 0.969 | 0.964 | 0.959 |
|29.5 | 0.988 | 0.983 | 0.978 | 0.973 | 0.968 | 0.962 |
|29.6 | 0.992 | 0.986 | 0.981 | 0.976 | 0.971 | 0.966 |
|29.7 | 0.995 | 0.990 | 0.985 | 0.980 | 0.974 | 0.969 |
|29.8 | 0.998 | 0.993 | 0.988 | 0.983 | 0.978 | 0.972 |
|29.9 | 1.002 | 0.997 | 0.991 | 0.986 | 0.981 | 0.976 |
|30.0 | 1.005 | 1.000 | 0.995 | 0.990 | 0.985 | 0.979 |
|30.1 | 1.009 | 1.003 | 0.998 | 0.993 | 0.988 | 0.983 |
|30.2 | 1.012 | 1.007 | 1.002 | 0.996 | 0.991 | 0.986 |
|30.3 | 1.015 | 1.010 | 1.005 | 1.000 | 0.995 | 0.989 |
|30.4 | 1.019 | 1.014 | 1.008 | 1.003 | 0.998 | 0.993 |
|30.5 | 1.022 | 1.017 | 1.012 | 1.006 | 1.001 | 0.996 |
|_____|_______|_______|_______|_______|_______|_______|
_____________________________________________
| | |
| | THERMOMETER. |
| BAR.|_______________________________________|
| | | | | | |
| | 70 | 72 | 74 | 76 | 78 |
| | deg. | deg. | deg. | deg. | deg. |
|_____|_______|_______|_______|_______|_______|
| | | | | | |
|28.4 | 0.921 | 0.915 | 0.910 | 0.905 | 0.900 |
|28.5 | 0.924 | 0.919 | 0.914 | 0.908 | 0.903 |
|28.6 | 0.927 | 0.922 | 0.917 | 0.912 | 0.906 |
|28.7 | 0.931 | 0.925 | 0.920 | 0.915 | 0.909 |
|28.8 | 0.934 | 0.929 | 0.924 | 0.918 | 0.913 |
|28.9 | 0.937 | 0.932 | 0.927 | 0.921 | 0.916 |
|29.0 | 0.941 | 0.935 | 0.930 | 0.925 | 0.919 |
|29.1 | 0.944 | 0.939 | 0.933 | 0.928 | 0.923 |
|29.2 | 0.947 | 0.942 | 0.937 | 0.931 | 0.926 |
|29.3 | 0.950 | 0.945 | 0.940 | 0.935 | 0.929 |
|29.4 | 0.954 | 0.949 | 0.943 | 0.938 | 0.932 |
|29.5 | 0.957 | 0.952 | 0.947 | 0.941 | 0.936 |
|29.6 | 0.960 | 0.955 | 0.950 | 0.944 | 0.939 |
|29.7 | 0.964 | 0.959 | 0.953 | 0.948 | 0.942 |
|29.8 | 0.967 | 0.962 | 0.957 | 0.951 | 0.946 |
|29.9 | 0.970 | 0.965 | 0.960 | 0.954 | 0.949 |
|30.0 | 0.974 | 0.968 | 0.963 | 0.958 | 0.952 |
|30.1 | 0.977 | 0.972 | 0.966 | 0.961 | 0.955 |
|30.2 | 0.980 | 0.975 | 0.970 | 0.964 | 0.959 |
|30.3 | 0.984 | 0.978 | 0.973 | 0.968 | 0.962 |
|30.4 | 0.987 | 0.982 | 0.976 | 0.971 | 0.965 |
|30.5 | 0.990 | 0.985 | 0.980 | 0.974 | 0.969 |
|_____|_______|_______|_______|_______|_______|

For the detection of phosphine, Berge's solution may be used. It is a
"solution of 8 to 10 parts of corrosive sublimate in 80 parts of water
and 20 parts of 30 per cent. hydrochloric acid." It becomes cloudy when
gas containing phosphine is passed into it. It is, however, applied most
conveniently in the form of Keppeler's test-papers, which have been
described in Chapter V. Test-papers for phosphine, the active body in
which has not yet been divulged, have recently been produced for sale by
F. B. Gatehouse.

The estimation of phosphine will usually require to be carried out either
(1) on gas directly evolved from carbide in order to ascertain if the
carbide in question yields an excessive proportion of phosphine, or (2)
upon acetylene which is presumably purified, drawn either from the outlet
of the purifier or from the service-pipes, with the object of
ascertaining whether an adequate purification in regard to phosphine has
been accomplished. In either case, the method of estimation is the same,
but in the first, acetylene should be specially generated from a small
representative sample of the carbide and led directly into the apparatus
for the absorption of the phosphine. If the acetylene passes into the
ordinary gasholder, the amount of phosphine in gas drawn off from the
holder will vary from time to time according to the temperature and the
degree of saturation of the water in the holder-tank with phosphine, as
well as according to the amount of phosphine in the gas generated at the
time.

A method frequently employed for the determination of phosphine in
acetylene is one devised by Lunge and Cedercreutz. If the acetylene is to
be evolved from a sample of carbide in order to ascertain how much
phosphine the latter yields to the gas, about 50 to 70 grammes of the
carbide, of the size of peas, are brought into a half-litre flask, and a
tap-funnel, with the mouth of its stem contracted, is passed through a
rubber plug fitting the mouth of the flask. A glass tube passing through
the plug serves to convey the gas evolved to an absorption apparatus,
which is charged with about 75 c.c. of a 2 to 3 per cent. solution of
sodium hypochlorite. The absorption apparatus may be a ten-bulbed
absorption tube or any convenient form of absorption bulbs which subject
the gas to intimate contact with the solution. If acetylene from a
service-pipe is to be tested, it is led direct from the nozzle of a gas-
tap to the absorption tube, the outlet of which is connected with an
aspirator or the inlet of an experimental meter, by which the volume of
gas passed through the solution is measured. But if the generating flask
is employed, water is allowed to drop from the tap-funnel on to the
carbide in the flask at the rate of 6 to 7 drops a minute (the tap-funnel
being filled up from time to time), and all the carbide will thus be
decomposed in 3 to 4 hours. The flask is then filled to the neck with
water, and disconnected from the absorption apparatus, through which a
little air is then drawn. The absorbing liquid is then poured, and washed
out, into a beaker; hydrochloric acid is added to it, and it is boiled in
order to expel the liberated chlorine. It is then usual to precipitate
the sulphuric acid by adding solution of barium chloride to the boiling
liquid, allowing it to cool and settle, and then filtering. The weight of
barium sulphate obtained by ignition of the filter and its contents,
multiplied by 0.137, gives the amount of sulphur present in the acetylene
in the form of sulphuretted hydrogen. The filtrate and washings from this
precipitate are rendered slightly ammoniacal, and a small excess of
"magnesia mixture" is added; the whole is stirred, left to stand for 12
hours, filtered, the precipitate washed with water rendered slightly
ammoniacal, dried, ignited, and weighed. The weight so found multiplied
by 0.278 gives the weight of phosphorus in the form of phosphine in the
volume of gas passed through the absorbent liquid.

Objection may rightly be raised to the Lunge and Cedercreutz method of
estimating the phosphine in crude acetylene on the ground that explosions
are apt to occur when the gas is being passed into the hypochlorite
solution. Also it must be borne in mind that it aims at estimating only
the phosphorus which is contained in the gas in the form of phosphine,
and that there may also be present in the gas organic compounds of
phosphorus which are not decomposed by the hypochlorite. But when the
acetylene is evolved from the carbide in proper conditions for the
avoidance of appreciable heating it appears fairly well established that
phosphorus compounds other than phosphine exist in the gas only in
practically negligible amount, unless the carbide decomposed is of an
abnormal character. Various methods of burning the acetylene and
estimating the phosphorus in the products of combustion have, however
been proposed for the purpose of determining the total amount of
phosphorus in acetylene. Some of them are applicable to the simultaneous
determination of the total sulphur in the acetylene, and in this respect
become akin to the Gas Referees' method for the determination of the
sulphur compounds in coal-gas.

Eitner and Keppeler have proposed to burn the acetylene on which the
estimation is to be made in a current of neat oxygen. But this procedure
is rather inconvenient, and by no means essential. Lidholm liberated
acetylene slowly from 10 grammes of carbide by immersing the carbide in
absolute alcohol and gradually adding water, while the gas mixed with a
stream of hydrogen leading to a burner within a flask. The flow of
hydrogen was reduced or cut off entirely while the acetylene was coming
off freely, but hydrogen was kept burning for ten minutes after the flame
had ceased to be luminous in order to ensure the burning of the last
traces of acetylene. The products of combustion were aspirated through a
condenser and a washing bottle, which at the close were rinsed out with
warm solution of ammonia. The whole of the liquid so obtained was
concentrated by evaporation, filtered in order to remove particles of
soot or other extraneous matter, and acidified with nitric acid. The
phosphoric acid was then precipitated by addition of ammonium molybdate.

J. W. Gatehouse burns the acetylene in an ordinary acetylene burner of
from 10 to 30 litres per hour capacity, and passes the products of
combustion through a spiral condensing tube through which water is
dropped at the rate of about 75 c.c. per hour, and collected in a beaker.
The burner is placed in a glass bell-shaped combustion chamber connected
at the top through a right-angled tube with the condenser, and closed
below by a metal base through which the burner is passed. The amount of
gas burnt for one determination is from 50 to 100 litres. When the gas is
extinguished, the volume consumed is noted, and after cooling, the
combustion chamber and condenser are washed out with the liquid collected
in the beaker and finally with distilled water, and the whole, amounting
to about 400 c.c., is neutralised with solution of caustic alkali (if
decinormal alkali is used, the total acidity of the liquid thus
ascertained may be taken as a convenient expression of the aggregate
amount of the sulphuric, phosphoric and silicic acids resulting from the
combustion of the total corresponding impurities in the gas), acidified
with hydrochloric acid, and evaporated to dryness with the addition
towards the end of a few drops of nitric acid. The residue is taken up in
dilute hydrochloric acid; and silica filtered off and estimated if
desired. To the filtrate, ammonia and magnesia mixture are added, and the
magnesium pyrophosphate separated and weighed with the usual precautions.
Sulphuric acid may, if desired, be estimated in the filtrate, but in that
case care must be taken that the magnesia mixture used was free from it.

Mauricheau-Beaupre has elaborated a volumetric method for the estimation
of the phosphine in crude acetylene depending on its decomposition by a
known volume of excess of centinormal solution of iodine, addition of
excess of standard solution of sodium thiosulphate, and titrating back
with decinormal solution of iodine with a few drops of starch solution as
an indicator. One c.c. of centinormal solution of iodine is equivalent to
0.0035 c.c. of phosphine. This method of estimation is quickly carried
out and is sufficiently accurate for most technical purposes.

In carrying out these analytical operations many precautions have to be
taken with which the competent analyst is familiar, and they cannot be
given in detail in this work, which is primarily intended for ordinary
users of acetylene, and not for the guidance of analysts. It may,
however, be pointed out that many useful tests in connexion with
acetylene supply can be conducted by a trained analyst, which are not of
a character to be serviceable to the untrained experimentalist. Among
such may be named the detection of traces of phosphine in acetylene which
has passed through a purifier with a view to ascertaining if the
purifying material is exhausted, and the estimation of the amount of air
or other diluents in stored acetylene or acetylene generated in a
particular manner. Advice on these points should be sought from competent
analysts, who will already have the requisite information for the
carrying out of any such tests, or know where it is to be found. The
analyses in question are not such as can be undertaken by untrained
persons. The text-book on "Gas Manufacture" by one of the authors gives
much information on the operations of gas analysis, and may be consulted,
along with Hempel's "Gas Analysis" and Winkler and Lunge's "Technical Gas
Analysis."

APPENDIX

DESCRIPTIONS OF A NUMBER OF ACETYLENE GENERATORS AS MADE IN THE YEAR 1909

(_The purpose of this Appendix is explained in Chapter IV., page 111,
and a special index to it follows the general index at the end of this
book._)

AMERICA--CANADA.

_Maker_: SICHE GAS CO., LTD., GEORGETOWN, ONTARIO.

_Type_: Automatic; carbide-to-water.

The "Siche" generator made by this firm consists of a water-tank
_A_, having at the bottom a sludge agitator _N_ and draw-off
faucet _O_, and rigidly secured within it a bell-shaped generating
chamber _B_, above which rises a barrel containing the feed chamber
_C_, surmounted by the carbide chamber _D_. The carbide used is
granulated or of uniform size. In the generating chamber _B_ is an
annular float _E_, nearly filling the area of the chamber, and
connected, by two rods passing, with some lateral play, through apertures
in the conical bottom of the feed chamber _C_, to the T-shaped
tubular valve _F_. Consequently when the float shifts vertically or
laterally the rods and valves at once move with it. The angle of the cone
of the feed chamber and the curve of the tubular valve are based on the
angle of rest of the size of carbide used, with the object of securing
sensitiveness of the feed. The feed is thus operated by a very small
movement of the float, and consequently there is but very slight rise and
fall of the water in the generating chamber. Owing to the lateral play,
the feed valve rarely becomes concentric with its seat. There is a cover
_G_ over the feed valve _F_, designed to distribute the carbide
evenly about the feed aperture and to prevent it passing down the hollow
of the valve and the holes through which the connecting-rods pass. It
also directs the course of the evolved gas on its way to the service-pipe
through the carbide in the feed chamber _C_, whereby the gas is
dried. The carbide chamber _D_ has at its bottom a conical valve,
normally open, but closed by means of the spindle _H_, which is
engaged at its upper end by the closing screw-cap _J_, which is
furnished with a safelocking device to prevent its removal until the
conical valve is closed and the hopper chamber _D_ thereby cut off
from the gas-supply. The cap _J_, in addition to a leather washer to
make a gas-tight joint when down, has a lower part fitting to make an
almost gas-tight joint. Thus when the cap is off; the conical valve fits
gas-tight; when it is on and screwed down it is gas-tight; and when on
but not screwed down, it is almost gas-tight. Escape of gas is thus
avoided. A special charging funnel _K_, shown in half-scale, is
provided for inserting in place of the screw cap. The carbide falls from
the funnel into the chamber _D_ when the chain is pulled. A fresh
charge of carbide may be put in while the apparatus is in action. The
evolved gas goes into the chamber _C_ through a pipe, with cock, to
a dust-arrester _L_, which contains a knitted stocking lightly
filled with raw sheep's wool through which the gas passes to the service-
pipe. The dust-arrester needs its contents renewing once in one, two, or
three years, according to the make of gas. The pressure of the gas is
varied as desired by altering the height of water in the tank _A_.
When cleaning the machine, the water must never be run below the top of
the generating chamber.

[Illustration: FIG. 24.--"SICHE" GENERATOR.]

AMERICA--UNITED STATES.

_Maker:_ J. B. COLT CO., 21 BARCLAY STREET, NEW YORK.

_Type:_ Automatic; carbide-to-water.

The "Colt" generator made by this firm comprises a carbide hopper mounted
above a generating tank containing water, and an equalising bell
gasholder mounted above a seal-pot having a vent-pipe _C_
communicating with the outer air. The carbide hopper is charged with 1/4
x 1/12 inch carbide, which is delivered from it into the water in the
generating tank in small portions at a time through a double valve, which
is actuated through levers connected to the crown of the equalising
gasholder. As the bell of the gasholder falls the lever rotates a rock
shaft, which enters the carbide hopper, and through a rigidly attached
lever raises the inner plunger of the feed-valve. The inner plunger in
turn raises the concentric outer stopper, thereby leaving an annular
space at the base of the carbide hopper, through which a small delivery
of carbide to the water in the generating tank then ensues. The gas
evolved follows the course shown by the arrows in the figure into the
gasholder, and raises the bell, thereby reversing the action of the
levers and allowing the valve to fall of its own weight and so cut off
the delivery of carbide. The outer stopper of the valve descends before
the inner plunger and so leaves the conical delivery mouth of the hopper
free from carbide. The inner plunger, which is capped at its lower end
with rubber, then falls and seats itself moisture-tight on the clear
delivery mouth of the hopper. The weight of the carbide in the hopper is
taken by its sides and a projecting flange of the valve casing, so that
the pressure of the carbide at the delivery point is slight and uniform.
The outside of the delivery mouth is finished by a drip collar with
double lip to prevent condensed moisture creeping upwards to the carbide
in the hopper. A float in the generating tank, by its descent when the
water falls below a certain level, automatically draws a cut off across
the delivery mouth of the carbide hopper and so prevents the delivery of
carbide either automatically or by hand until the water in the generating
tank has been restored to its proper level. Interlocking levers, (11) and
(12) in the figure, prevent the opening of the feed valve while the cap
(10) of the carbide hopper is open for recharging the hopper. There is a
stirrer actuated by a handle (9) for preventing the sludge choking the
sludge cock. The gas passes into the gasholder through a floating seal,
which serves the dual purpose of washing it in the water of the gasholder
tank and of preventing the return of gas from the holder to the
generating tank. From the gasholder the gas passes to the filter (6)
where it traverses a strainer of closely woven cotton felt for the
purpose of the removal of any lime.

[Illustration: FIG. 25.--"COLT" GENERATING PLANT.]

Drip pipes (30) and (31) connected to the inlet- and outlet-pipes of the
gasholder are sealed in water to a depth of 6 inches, so that in the
event of the pressure in the generator or gasholder rising above that
limit the surplus gas blows through the seal and escapes through the
vent-pipe _C_. There is also a telescopic blow-off (32) and (33),
which automatically comes into play if the gasholder bell rises above a
certain height.

_Maker:_ DAVIS ACETYLENE CO., ELKHARDT, INDIANA.

_Type:_ Automatic; carbide-to-water.

The "Davis" generator made by this firm comprises an equalising bell
gasholder with double walls, the inner wall surrounding a central tube
rising from the top of the generating chamber, in which is placed a
water-sealed carbide chamber with a rotatory feeding mechanism which is
driven by a weight motor. The carbide falls from the chamber on to a wide
disc from which it is pushed off a lump at a time by a swinging
displacer, so arranged that it will yield in every direction and prevent
clogging of the feeding mechanism. Carbide falls from the disk into the
water of the generating chamber, and the evolved gas raises the bell and
so allows a weighted lever to interrupt the action of the clockwork,
until the bell again descends. The gas passes through a washer in the
gasholder tank, and then through an outside scrubber to the service-pipe.
There is an outside chamber connected by a pipe with the generating
chamber, which automatically prevents over-filling with water, and also
acts as a drainage chamber for the service- and blow-off-pipes. There is
an agitator for the residuum and a sludge-cock through which to remove
same. The feeding mechanism permits the discharge of lump carbide, and
the weight motor affords independent power for feeding the carbide, at
the same time indicating the amount of unconsumed carbide and securing
uniform gas pressure.

[Illustration: FIG. 26.--"DAVIS" GENERATOR.]

_Maker:_ SUNLIGHT GAS MACHINE CO., 49 WARREN STREET, NEW YORK.

_Type:_ Automatic; carbide-to-water.

The "Omega" apparatus made by this firm consists of a generating tank
containing water, and surmounted by a hopper which is filled with carbide
of 1/4-inch size. The carbide is fed from the hopper into the generating
tank through a mechanism consisting of a double oscillating cup so
weighted that normally the feed is closed. The fall of the bell of the
equalising gasholder, into which the gas evolved passes, operates a lever
_B_, which rotates the weighted cup in the neck of the hopper and so
causes a portion of carbide to fall into the water in the generating
tank. The feed-cup consists of an upper cup into which the carbide is
first delivered. It is then tipped from the upper cup into the lower cup
while, at the same time, further delivery from the hopper is prevented.
Thus only the portion of carbide which has been delivered into the lower
cup is emptied at one discharge into the generator. There is a safety
lock to the hopper cap which prevents the feeding mechanism coming into
operation until the hopper cap is screwed down tightly. Provision is made
for a limited hand-feed of carbide to start the apparatus. The gasholder
is fitted with a telescoping vent-pipe, by which gas escapes to the open
in the event of the bell being raised above a certain height. There is
also an automatic cut-off of the carbide feed, which comes into operation
it the gas is withdrawn too rapidly whether through leakage in the pipes
or generating plant, or through the consumption being increased above the
normal generating capacity of the apparatus. The gas evolved passes into
a condensing or washing chamber placed beneath the gasholder tank and
thence it travels to the gasholder. From the gasholder it goes through a
purifier containing "chemically treated coke and cotton" to the supply-pipe.

[Illustration: FIG. 27.--"OMEGA" GENERATOR.]

1 Vent-cock handle.
2 Residuum-cock handle.
3 Agitator handle.
4 Filling funnel.
5 Water overflow.
6 Hopper cap and lever.
7 Starting feed.
8 Rocker arm.
9 Feed connecting-rod.
A Pawl.
B Lever for working feed mechanism.
C Guide frame.
D Residuum draw-off cock.
G Chain from hopper cap to feed mechanism.
H Blow-off and vent-pipe connexion.
I Gas outlet from generator.
J Gas service-cock.
K Filling funnel for gasholder tank.
L Funnel for condensing chamber.
M Gas outlet at top of purifier.
N Guides on gas-bell.
O Crosshead on swinging pawl.
P Crane carrying pawl.
Q Shaft connecting feed mechanism.
R Plug in gas outlet-pipe.
S Guide-frame supports.
U Removable plate to clean purifier.
Z Removable plate to expose feed-cups for cleaning same.

AUSTRIA-HUNGARY

_Maker:_ RICH. KLINGER, GUMPOLDSKIRCHEN, NEAR VIENNA.

_Type:_ Non-automatic; carbide-to-water.

The generating plant made by this firm consists of the generator _A_
which is supported in a concrete water and sludge tank _B_, a
storage gasholder _J_, and purifiers _K_. In the top of the
generator are guide-ways _F_, through each of which is passed a
plunger _C_ containing a perforated cage charged with about 8 lb. of
lump carbide. The plungers are supported by ropes passing over pulleys
_D_, and when charged they are lowered through the guide-ways
_F_ into the water in the tank _B_. The charge of carbide is
thus plunged at once into the large body of water in the tank, and the
gas evolved passes through perforations in the washer _G_ to the
condenser _H_ and thence to the storage gasholder _J_. After
exhaustion of the charge the plungers are withdrawn and a freshly charged
cage of carbide inserted ready for lowering into the generating tank.
There is a relief seal _f_ through which gas will blow and escape by
a pipe _g_ to the open should the pressure within the apparatus
exceed the depth of the seal, viz., about 9 inches. There is a syphon pot
_N_ for the collection and withdrawal of condensed water. The sludge
is allowed to accumulate in the bottom of the concrete tank _B_
until it becomes necessary to remove it at intervals of about three
months. Water is added to the tank daily to replace that used up in the
generation of the gas. The gas passes from the storage holder through one
of the pair of purifiers _K_, with water-sealed lids, which are
charged with a chemical preparation for the removal of phosphoretted
hydrogen. This purifying material also acts as a desiccating agent. From
the purifiers the gas passes through the meter _L_ to the service-
pipes.

[Illustration: FIG. 28.--KLINGER'S GENERATING PLANT.]

BELGIUM.

_Maker_: SOC. AN. DE L'ACETYLITHE, 65 RUE DU MARCHE, BRUSSELS.

_Type_: Automatic; contact.

The generating apparatus made by this firm uses, instead of ordinary
carbide, a preparation known as "acetylithe," which is carbide treated
specially with mineral oil, glucose and sugar. The object of using this
treated carbide is to avoid the effects of the attack of atmospheric
humidity or water vapour, which, with ordinary carbide, give rise to the
phenomena of after-generation. The generator comprises a water-tank
_A_ with conical base, a basket _C_ containing the treated
carbide inserted within a cylindrical case _B_ which is open at the
bottom and is surmounted by a cylindrical filter _D_. At starting,
the tank _A_ is filled with water to the level _N N'_. The
water rises within the cylindrical case until it comes in contact with
the treated carbide, which thereupon begins to evolve gas. The gas passes
through the filter _D_, which is packed with dry cotton-wool, and
escapes through the tap _M_. As soon as the contained air has been
displaced by gas the outlet of the tap _M_ is connected by a
flexible tube to the pipe leading to a purifier and the service-pipe.
When the tap _M_ is closed, or when the rate of evolution of the gas
exceeds the rate of consumption, the evolved gas accumulates within the
cylindrical case _B_ and begins to displace the water, the level of
which within the case is lowered from _S S'_, first to _S1 S'1_
and ultimately to, say, _S2 S'2_. The evolution of gas is thereby
gradually curtailed or stopped until more is required for consumption.
The water displacement causes the water-level in the outer tank to rise
to _N1 N'1_ and ultimately to, say _N2 N'2_. The lime formed by
the decomposition of the carbide is loosened from the unattacked portion
and taken more or less into solution as sucrate of lime, which is a
soluble salt which the glucose or sugar in the treated carbide forms with
lime. The solution is eventually run off through the cock _R_. The
cover _T_ of the filter is screwed down on rubber packing until gas-
tight. The purifier is charged with puratylene or other purifying
material.

[Illustration: FIG. 29.--ACETYLITHE GENERATOR.]

_Maker_: L. DEBRUYNE, 22 PLACE MASUI, BRUSSELS.

_Type_: (1) Automatic; carbide-to-water.

The generating plant made by this firm, using granulated carbide,
comprises an equalising gasholder _E_ alongside a generating tank
_B_, which is surmounted by a closed carbide receptacle _A_ and
a distributing appliance. The carbide receptacle is filled with
granulated carbide and the lid _N_ screwed down; the carbide is then
withdrawn from the base of the receptacle by the distributing appliance
and discharged in measured quantities as required into the water in the
generating tank. The distributing appliance is actuated by a weighted
cord _H_ attached to the bell _I_ of the gasholder and
discharges at each time a quantity of carbide only sufficient nearly to
fill the gasholder with acetylene. The gas passes from the generator
through the pipe _J_ and seal-pot _D_, or bypass _F_, to
the gasholder. The generating tank is provided with a funnel _G_ for
replacing the water consumed, a sludge-stirrer and a draw-off cock
_L_, and a water-level cock _C_. The gas passes from the
gasholder through a purifier _K_, charged with heratol, to the
service-pipe.

[Illustration: FIG. 30.--L. DEBRUYNE'S GENERATING PLANT FOR GRANULATED
CARBIDE.]

(2) Automatic; carbide-to-water.

The "Debruyne" generator comprises an equalising bell gasholder _A_
placed alongside a generating tank _B_ containing water into which
lump carbide is discharged as necessary from each in turn of a series of
chambers mounted in a ring above the generating tank. The chambers are
removable for refilling, and when charged are hermetically sealed until
opened in turn above the shoot _C_, through which their contents are
discharged into the generating tank. The carbide contained in each
chamber yields sufficient gas nearly to fill the gasholder. The
discharging mechanism is operated through an arm _E_ attached to the
bell _G_ of the gasholder, which sets the mechanism in motion when
the bell has fallen nearly to its lowest position. The lip _L_
serves for renewing the water in the generator, and the gas evolved goes
through the pipe _K_ with tap _F_ to the gasholder. There is an
eccentric stirrer for the sludge and a large-bore cock for discharging
it. The gas passes from the gasholder through the pipe _J_ to the
purifier _H_, charged with heratol, and thence to the service-pipe.

[Illustration: FIG. 3l.--THE "DEBRUYNE" GENERATING PLANT FOR LUMP
CARBIDE.]

_Maker_: DE SMET VAN OVERBERGE, ALOST.

_Type_: (1) Automatic; carbide-to-water.

This generating apparatus comprises an equalising gasholder _A_
placed alongside a generating tank _B_, above which is mounted on a
rotating spindle a series of chambers _C_, arranged in a circle,
which are filled with carbide. The generating tank is closed at the top,
but on one side there is a shoot _D_ through which the carbide is
discharged from the chambers in turn into the water in the tank. The
series of chambers are rotated by means of a cord passing round a pulley
_E_ and having a weight _F_ at one end, and being attached to
the bell of the gasholder at the other. When the bell falls, owing to the
consumption of gas, to a certain low position, the carbide chamber, which
has been brought by the rotation of the pulley over the shoot, is opened
at the bottom by the automatic liberation of a catch, and its contents
are discharged into the generating tank. The contents of one carbide
chamber suffice to fill the gasholder to two-thirds of its total
capacity. The carbide chambers after filling remain hermetically closed
until the bottom is opened for the discharge of the carbide. There is a
sludge-cock _G_ at the bottom of the generating tank. The gas passes
from the gasholder through a purifier _H_, which is ordinarily
charged with puratylene.

[Illustration: FIG. 32.--AUTOMATIC GENERATING PLANT OF DE SMET VAN
OVERBERGE.]

(2) Non-automatic; carbide-to-water.

This apparatus comprises a storage bell gasholder _J_ placed
alongside a generating tank in the top of which is a funnel _E_ with
a counter-weighted lever pivoted on the arm _B_. The base of the
funnel is closed by a flap valve _C_ hinged at _D_. When it is
desired to generate gas the counter-weight _A_ of the lever is
raised and the valve at the bottom of the funnel is thereby opened. A
charge of carbide is then tipped into the funnel and drops into the water
in the generating tank. The valve is then closed and the gas evolved goes
through the pipe _G_ to the gasholder, whence it passes through a
purifier to the service-pipe. There is a sludge-cock on the generating
tank.

[Illustration: FIG. 33.--NON-AUTOMATIC GENERATING PLANT OF DE SMET VAN
OVERBERGE.]

_Maker_: SOC. AN. BELGE DE LA PHOTOLITHE, 2 RUE DE HUY, LIEGE.

_Type_: Automatic; carbide-to-water.

The "Photolithe" generating plant made by this firm comprises an
equalising bell gasholder _A_ in the tank _O_, alongside a
generating tank _B_ which is surmounted by a carbide storage
receptacle divided into a number of compartments. These compartments are
fitted with flap bottoms secured by catches, and are charged with
carbide. Through the middle of the storage receptacle passes a spindle,
to the upper end of which is attached a pulley _b_. Round the pulley
passes a chain, one end of which carries a weight _n_, while in the
other direction it traverses guide pulleys and is attached to a loop on
the crown of the gasholder bell. When the bell falls below a certain
point owing to the consumption of gas, it pulls the chain and rotates the
pulley _b_ and therewith an arm _d_, which liberates the catch
supporting the flap-bottom of the next in order of the carbide
compartments. The contents of this compartment are thereby discharged
through the shoot _C_ into the generating tank _B_. The gas
evolved passes through the cock _R_ and the pipe _T_ into the
gasholder, the rise of the bell of which takes the pull off the chain and
allows the weight at its other end to draw it up until it is arrested by
the stop _f_. The arm _d_ is thereby brought into position to
liberate the catch of the next carbide receptacle. The generating tank is
enlarged at its base to form a sludge receptacle _E_, which is
provided with a sludge draw-off cock _S_ and a hand-hole _P_.
Between the generating tank proper and the sludge receptacle is a grid,
which is cleaned by means of a rake with handle _L_. The gas passes
from the gasholder through a purifier _H_ charged with puratylene,
to the service-pipe.

[Illustration: FIG. 34.--"PHOTOLITHE" GENERATING PLANT.]

The same firm also makes a portable generating apparatus in which the
carbide is placed in a basket in the crown of the bell of the gasholder.
This apparatus is supplied on a trolley for use in autogenous soldering
or welding.

FRANCE.

_Maker_: LA SOC. DES APPLICATIONS DE L'ACETYLENE, 26 RUE CADET,
PARIS.

_Type_: Automatic; carbide-to-water.

The "Javal" generating plant made by this firm consists of an equalising
bell gasholder _A_ in the tank _B_ with a series of buckets
_D_, with removable bottoms _h_, mounted on a frame _F_
round the guide framing of the holder. Alongside the gasholder stands the
generating tank _H_ with shoot _K_, into which the carbide
discharged from the buckets falls. On top of the generator is a tipping
water-bucket _I_ supplied with water through a ball cock. The bell
of the gasholder is connected by chains _a_ and _c_, and levers
_b_ and _d_ with an arm which, when the bell descends to a
certain point, comes in contact with the catch by which the bottom of the
carbide bucket is held in place, and, liberating the same, allows the
carbide to fall into the shoot. When the bell rises, in consequence of
the evolved gas, the ring of carbide buckets is rotated sufficiently to
bring the next bucket over the shoot. Thus the buckets are discharged in
turn as required through the rise and fall of the gasholder bell.

[Illustration: FIG. 35.--"JAVAL" GENERATOR.]

The carbide falling from the opened bucket strikes the end _i_ of
the lever _k_, and thereby tips the water-bucket _I_ and
discharges its contents into the shoot of the generator. The rise in the
level of the water in the generator, due to the discharge of the water
from the bucket _I_, lifts the float _L_ and therewith, through
the attached rod and chain _u_, the ball _s_ of the valve
_t_. The sludge, which has accumulated in the base _N_ of the
generator from the decomposition of the previous portion of carbide, is
thereby discharged automatically into a special drain. The discharge-
valve closes automatically when the float _L_ has sunk to its
original level. The gas evolved passes from the generator through the
seal-pot _M_ and the pipe _r_ with cock _q_ into the
gasholder, from which it passes through the pipe _x_; with
condensation chamber and discharge tap _y_ into the purifier
_R_, which is charged with heratol.

_Maker_: L'HERMITE, LOUVIERS, EURE.

_Type_: (1) Automatic; carbide-to-water.

The generating plant known as "L'Eclair," by this firm comprises an
equalising bell gasholder _A_ floating in an annular water-seal
_N_, formed in the upper part of a generating tank _B_ into
which carbide enters through the shoot _K_. Mounted at the side of
the tank is the carbide delivery device, which consists of the carbide
containers _J_ supported on an axis beneath the water-sealed cover
_H_. The containers are filled with ordinary lump carbide when the
cover _H_ is removed. The tappet _O_ attached to the bell of
the gasholder come in contact with a pawl when the gasholder bell
descends to a certain level and thereby rotates a pinion on the
protruding end of the axis which carries the carbide containers _J_.
Each time the bell falls and the tappet strikes the pawl, one compartment
of the carbide containers discharges its contents down the shoot _K_
into the generating tank _B_. The gas evolved passes upwards and
causes the bell _A_ to rise. The gas is prevented from rising into
the shoot by the deflecting plates _G_. The natural level of the
water in the generating tank, when the apparatus is in use, is shown by
the dotted lines _L_. The lime sludge is discharged from time to
time through the cock _E_, being stirred up by means of the agitator
_C_ with handle _D_. When the sludge is discharged water is
added through _M_ to the proper level. The gas evolved passes from
the holder through the pipe with tap _F_ to the service-pipe. A
purifier is supplied if desired.

[Illustration: FIG. 36.--"L'ECLAIR," GENERATOR.]

_References_

A Gasholder.
B Generator.
C Agitator.
D Handle of agitator.
E Sludge-cock.
F Gas outlet.
G Deflecting plates.
H Cover.
I Carbide.
J Automatic distributor.
K Shoot.
L Water-level.
M Water-inlet.
N Water-seal.
O Tappet.

(2) Automatic; water-to-carbide; contact.

A generating plant known as "L'Etoile" made by this firm. A tappet on the
bell of an equalising gasholder depresses a lever which causes water to
flow into a funnel, the outlet of which leads to a generating chamber
containing carbide.

_Maker_: MAISON SIRIUS, FR. MANGIAMELI & CO., 34 RUE DES PETITS-
HOTELS, PARIS.

_Type_: (1) Automatic; carbide-to-water.

The generating plant made by this firm comprises a drum-shaped carbide
holder mounted above a generating tank, a condenser, a washer, an
equalising gasholder, and a purifier. The drum _A_ is divided into
eight chambers _a_ each closed by a fastening on the periphery of
the drum. These chambers are packed with lump carbide, which is
discharged from them in turn through the funnel _B_ into the
generating tank, which is filled with water to the level of the overflow
cock _b_. A deflecting plate _d_ in the tank distributes the
carbide and prevents the evolved gas passing out by way of the funnel
_B_. The gas evolved passes through the pipe _O_ into the
condenser, which is packed with coke, through which the gas goes to the
pipe _E_ and so to the washer _P_ through the water, in which
it bubbles and issues by the pipe _G_ into the gasholder. The bell
_L_ of the gasholder is connected by a chain _C_ to the axis of
the drum _A_, on which is a pinion with pawl so arranged that the
pull on the chain caused by the fall of the bell of the gasholder rotates
the drum by 1/8 of a turn. The catch on the outside of the carbide
chamber, which has thereby been brought to the lowest position, is at the
same time freed, so that the contents of the chamber are discharged
through the funnel _B_. The evolved gas causes the bell to rise and
the drum remains at rest until, owing to the consumption of gas, the bell
again falls and rotates the drum by another 1/8 of a turn. Each chamber
of the drum holds sufficient carbide to make a volume of gas nearly equal
to the capacity of the gasholder. Thus each discharge of carbide very
nearly fills the gasholder, but cannot over-fill it. The bell is provided
with a vent-pipe _i_, which comes into operation should the bell
rise so high that it is on the point of becoming unsealed. From the
gasholder the gas passes through the pipe _J_, with cock _e_,
to the purifier, which is charged with frankoline, puratylene, or other
purifying material, whence it passes to the pipe _N_ leading to the
place of combustion. The generating tank is provided with a sludge-cock
_g_, and a cleaning opening with lid _f_. This generating plant
has been primarily designed for the use of acetylene for autogenous
welding, and is made also mounted on a suitable trolley for transport for
this purpose.

[Illustration: FIG. 37.--"SIRIUS" GENERATOR.]

(2) Automatic; carbide-to-water.

A later design of generating plant, known as the Type G, also primarily
intended for the supply of acetylene for welding, has the carbide store
mounted in the crown of the bell of the equalising gasholder, to the
framing of the tank of which are attached a purifier, charged with
frankoline, and a safety water-seal or valve. The whole plant is mounted
on a four-legged stand, and is provided with handles for carrying as a
whole without dismounting. It is made in two sizes, for charges of 5-1/2
and 11 lb. of carbide respectively.

GERMANY.

_Maker_: KELLER AND KNAPPICH, G.m.b.H., AUGSBURG.

_Type_: Non-automatic; carbide-to-water.

The "Knappich" generating plant made by this firm embodies a generating
tank, one-half of which is closed, and the other half of which is open at
the top, containing water. A small drum containing carbide is attached by
a clamp to the end of a lever which projects above the open half of the
tank. The lever is fastened to a horizontal spindle which is turned
through 180 deg. by means of a counter-weighted lever handle. The carbide
container is thus carried into the water within the closed half of the
tank, and is opened automatically in transit. The carbide is thus exposed
to the water and the evolved gas passes through a pipe from the top of
the generating tank to a washer acting on the Livesey principle, and
thence to a storage gasholder. The use of closed carbide containers in
charging is intended to preclude the introduction of air into the
generator, and the evolution and escape of gas to the air while the
carbide is being introduced. Natural circulation of the water in the
generating tank is encouraged with a view to the dissipation of heat and
washing of the evolved gas. From the gasholder the gas passes in a
downward direction through two purifiers arranged in series, charged with
a material supplied under the proprietary name of "Carburylen." This
material is stated to act as a desiccating as well as a purifying agent.
The general arrangement of the plant is shown in the illustration. (Fig.
38).

[Illustration: FIG. 38.--"KNAPPICH" GENERATING PLANT.]

_Maker_: NORDISCHE AZETYLEN-INDUSTRIE; ALTONA-OTTENSEN.

_Type_: Automatic; water-to-carbide; "drawer."

The apparatus made by this firm consists of an equalising gasholder with
bell _D_ and tank _E_, a water-tank _O_, and two drawer
generators _C_ situated in the base of the gasholder tank. The
water-supply from the tank _O_ through the pipe _P_ with valve
_Q_ is controlled by the rise and fall of the bell through the
medium of the weight _J_ attached to the bell. When the bell
descends this weight rests on _K_ and so moves a counter-weighted
lever, which opens the valve _Q_. The water then flows through the
nozzle _B_ into one division of the funnel _A_ and down the
corresponding pipe to one of the generators. The generators contain trays
with compartments intended to be half filled with carbide. The gas
evolved passes up the pipe _T_ and through the seal _U_ into
the bell of the gasholder. There is a safety pipe _F_, the upper end
of which is carried outside the generator house. From the gasholder the
gas is delivered through the cock _M_ to a purifier charged with a
special purifying material mixed with cork waste and covered with
wadding. There is a drainage cock _N_ at the base of the purifier.
The nozzle _B_ of the water-supply pipe is shifted to discharge into
either compartment of the funnel _A_, according to which of the two
generators is required to be in action. The other generator may then be
recharged without interfering with the continuous working of the plant.

[Illustration: FIG. 39.--GENERATING PLANT OF THE NORDISCHE AZETYLEN-
INDUSTRIE.]

GREAT BRITAIN AND IRELAND.

_Maker:_ THE ACETYLENE CORPORATION OF GREAT BRITAIN LTD., 49
VICTORIA STREET, LONDON, S.W.

_Type:_ (1) Automatic; water-to-carbide; contact, superposed pans.

The "A1" generating plant made by this firm comprises a bell gasholder,
with central guide, standing alongside the generator. The generator
consists of a rectangular tank in which is a generating chamber having a
water-sealed lid with pressure test-cock _I_. Into the generating
chamber fit a number of pans _J_, which are charged with carbide.
Water is supplied to the generating chamber from an overhead tank
_B_ through the starting tap _D_ and the funnel _E_. It
flows out of the supply-pipe near the top of the generating chamber
through a slot in the side of the pipe facing the corner of the chamber,
so that it runs down the latter without splashing the carbide in the
upper pans. It enters first the lowest carbide pan through the
perforations, which are at different levels in the side of the pan. It
thus attacks the carbide from the bottom upwards. The evolved gas passes
from the generating chamber through a pipe opening near the top of the
same to the washer _A_, which forms the base of the generating tank.
It bubbles through the water in the washer, which therefore also serves
as a water-seal, and passes thence to the gasholder. On the bell of the
gasholder is an arm _C_ which, when the holder descends nearly to
its lowest point, depresses the rod _C_, which is connected by a
chain to a piston in the outlet-pipe from the water-tank _B_. The
fall of the gasholder thereby raises the piston and allows water to flow
out of the tank _B_ through the tap _D_ to the funnel _E_.
The generating tank is connected by a pipe, with tap _G_, with the
washer _A_, and the water in the generating tank is run off through
this pipe each time the generating chamber is opened for recharging,
thereby flushing out the washer _A_ and renewing the water in the
same. There is a sludge discharging tap _F_. With a view to the
ready dissipation of the heat of generation the generating chamber is
made rectangular and is placed in a water-tank as described. Some of the
heat of generation is also communicated to the underlying washer and
warms the water in it, so that the washing of the gas is effected by warm
water. Water condensing in the gasholder inlet-pipe falls downwards to
the washer. There is a water lip _H_ by which the level of the water
in the washer is automatically kept constant. The gasholder is provided
with a safety-pipe _K_, which allows gas to escape through it to the
open before the sides of the holder become unsealed, should the holder
for any reason become over-filled. The holder is of a capacity to take
the whole of the gas evolved from the carbide in one pan, and the water-
tank _B_ holds just sufficient water for the decomposition of one
charge of the generator. From the gasholder the gas passes through a
purifier, which is ordinarily charged with "Klenzal," and a baffle-box
for abstraction of dust, to the service-pipe. With plants intended to
supply more than forty lights for six hours, two or more generating
chambers are employed, placed in separate compartments of one rectangular
generating tank. The water delivery from the water-tank _B_ then
takes place into a trough with outlets at different levels for each
generating chamber. By inspection of this trough it may be seen at once
whether the charge in any generating chamber is unattacked, in course of
attack, or exhausted.

[Illustration: FIG. 40.--THE "A1" GENERATING PLANT OF THE ACETYLENE
CORPORATION OF GREAT BRITAIN, LTD.]

(2) Automatic; water-to-carbide; contact.

The same firm also makes the "Corporation Flexible-Tube Generator," which
is less costly than the "A1" (_vide supra_). The supply of water to
the generating vessels takes place from the tank of the equalising bell
gasholder and is controlled by a projection on the bell which depresses a
flexible tube delivering into the generating vessels below the level of
the water inlet to the tube.

(3) Automatic; water-to-carbide; "drawer."

The same firm also makes a generator known as the "A-to-Z," which is less
costly than either of the above. In it water is supplied from the tank of
a bell gasholder to a drawer type of generator placed in the base of the
gasholder tank. The supply of water is controlled by an external piston-
valve actuated through the rise and fall of the bell of the gasholder.
The flow of water to the generator is visible.

_Maker_: THE ACETYLENE GAS AND CARBIDE OF CALCIUM CO., PONTARDAWE,
R.S.O., GLAM.

_Type_: Automatic; water-to-carbide; flooded compartment.

The "Owens" generator made by this firm comprises an equalising bell
gasholder alongside which are placed two or more inclined generating
cylinders. The front lower end of each cylinder is fitted with a lid
which is closed by a screw clamp. There is inserted in each cylinder a
cylindrical trough, divided into ten compartments, each of which contains
carbide. Water is supplied to the upper ends of the cylinders from a
high-level tank placed at the back of the gasholder. In the larger sizes
the tank is automatically refilled from a water service through a
ball-cock. The outlet-valve of this tank is operated through a counter-
weighted lever, the unweighted end of which is depressed by a loop,
attached to the crown of the gasholder bell, when the bell has nearly
reached its lowest position. This action of the bell on the lever opens
the outlet-valve of the tank and allows water to flow thence into one of
the generating cylinders. It is discharged into the uppermost of the
compartments of the carbide trough, and when the carbide in that
compartment is exhausted it flows over the partition into the next
compartment, and so on until the whole trough is flooded. The gas passes
from the generating cylinders through a water-seal and a baffle plate
condenser placed within the water link of the gasholder to the bell of
the latter. There is a water seal on the water supply-pipe from the tank
to the generators, which would be forced should the pressure within the
generators for any reason become excessive. There is also a sealed vent-
pipe which allows of the escape of gas from the holder to the open should
the holder for any reason be over filled. The gas passes from the holder
through a purifier charged with "Owens" purifying material to the service
pipe. The plant is shown in Fig 41.

[Illustration: FIG. 41.--"OWENS" GENERATOR.]

_Maker_ ACETYLENE ILLUMINATING CO, LTD, 268-270 SOUTH LAMBETH ROAD,
LONDON, SW

_Type_ (1) Non automatic, carbide to water

The generator _A_ of this type made by this firm is provided with a
loading box _B_, with gas tight lid, into which the carbide is put.
It is then discharged by moving a lever which tilts the hinged bottom
_D_ of the box _B_, and so tips the carbide through the shoot
_E_ on to the conical distributor _F_ and into the water in the
generating chamber. There is a sludge cock _G_ at the base of the
generator. Gas passes as usual from the generator to a washer and storage
gasholder. Heratol is the purifying material supplied.

[Illustration: FIG. 42.--CARBIDE-TO-WATER GENERATOR OF THE ACETYLENE
ILLUMINATING CO., LTD.]

(2) Non-automatic; water-to-carbide; contact.

The generator _A_ is provided with a carbide container with
perforated base, and water is supplied to it from a delivery-pipe through
a scaled overflow. The gas evolved passes through the pipe _E_ to
the washer _B_, which contains a distributor, and thence to the
storage gasholder _G_. There is a sludge-cock _F_ at the base
of the generator. From the gasholder the gas passes through the purifier
_D_, charged with heratol, to the service-pipe.

[Illustration: FIG. 43.--WATER-TO-CARBIDE GENERATING PLANT OF THE
ACETYLENE ILLUMINATING CO., LTD.]

_Maker_: THE ALLEN CO., 106 VICTORIA STREET, LONDON, S.W.

_Type_: Automatic; water-to-carbide; contact, superposed trays.

The generating plant made by this firm comprises an equalising bell
gasholder, from the tank of which water is supplied through a flexible
tube to the top of a water-scaled generating chamber in which is a
vertical cylinder containing a cage packed with carbide. The open end of
the flexible tube is supported by a projection from the bell of the
gasholder, so that as the bell rises it is raised above the level of the
water in the tank and so ceases to deliver water to the generator until
the bell again falls. The water supplied flows by way of the water-seal
of the cover of the generating chamber to the cylinder containing the
carbide cage. Larger sizes have two generating chambers, and the nozzle
of the water delivery-pipe may be switched over from one to the other.
There is an overflow connexion which brings the second chamber
automatically into action when the first is exhausted. One chamber may be
recharged while the other is in action. Spare cylinders and cages are
provided for use when recharging. There is a cock for drawing off water
condensing in the outlet-pipe from the gasholder. The gas passes from the
holder to the lower part of a purifier with water-scaled cover, through
the purifying material in which it rises to the outlet leading to the
service-pipe. Purifying material under the proprietary name of the
"Allen" compound is supplied. The plant is shown in Fig. 44.

[Illustration: FIG. 44.--"ALLEN" FLEXIBLE-TUBE GENERATOR.]

Maker: THE BON-ACCORD ACETYLENE GAS CO., 285 KING STREET, ABERDEEN.

Type: Automatic; water-to-carbide; contact, superposed trays.

The "Bon Accord" generating plant made by this firm comprises an
equalising displacement gasholder _B_ immersed in a water-tank
_A_. Alongside the tank are placed two water-jacketed generating
chambers _G1_ and _G2_ containing cages _K_ charged with
carbide. Water passes from within the gasholder through the water inlet-
pipes _L1 L2_, the cock _H_, and the pipes _F1 F2_ to the
generating chambers, from which the gas evolved travels to the holder
_B_, in which it displaces water until the water-level falls below
the mouths of the pipes _L1_ and _L2_, and so cuts off the
supply of water to the generating chambers. The gas passes from the
holder _B_ through the pipe with outlet-cock _T_ to a washer
containing an acid solution for the neutralisation of ammonia, then
through a purifier containing a "special mixture of chloride of lime."
After that through a tower packed with lime, and finally through a
pressure regulator, the outlet of which is connected to the service-pipe.
There is an indicator _I_ to show the amount of gas in the holder.
One generator may be charged while the other is in action.

[Illustration: FIG. 45.--"BON-ACCORD" GENERATOR.]

_Maker_: FREDK. BRABY AND CO., LTD., ASHTON GATE WORKS, BRISTOL; AND
352-364 EUSTON ROAD, LONDON.

_Type:_ (I) Automatic; carbide-to-water.

The "A" type of generator made by this firm comprises an equalising bell
gasholder, round the bell of which are arranged a series of buckets which
are charged with carbide. Those buckets are discharged in turn as the
bell falls from time to time through a mechanism operated by a weight
suspended from a wire cord on a revolving spindle. The carbide is
discharged on to a different spot in the generating tank from each
bucket. There is a cock for the periodical removal of sludge. Gas passes
through a purifier charged with puratylene to the service-pipe. The
disposition of the parts of the plant and the operating mechanism arc
shown in the accompanying figure, which represents the generating
apparatus partly in elevation and partly in section. The carbide buckets
(1) are loosely hooked on the flat ring (2) bolted to the gasholder tank
(3). The buckets discharge through the annular water-space (4) between
the tank and the generator (5). The rollers (6), fitted on the generator,
support a ring (7) carrying radial pins (8) projecting outwards, one pin
for each bucket. The ring can travel round on the rollers. Superposed on
the ring is a tray (9) closed at the bottom except for an aperture
beneath the throat (11), on which is mounted an inclined striker (12),
which strikes the projecting tongues (1_a_) of the lids of the
buckets in turn. There is fixed to the sides of the generator a funnel
(13) with open bottom (13_a_) to direct the carbide, on to the
rocking grid (14) which is farther below the funnel than appears from the
figure. Gas passing up behind the funnel escapes through a duct (15) to
the gasholder. The ring (7) is rotated through the action of the weight
(16) suspended by the chain or rope (17) which passes round the shaft
(18), which is supported by the bracket (19) and has a handle for winding
up. An escapement, with upper limb (20_a_) and lower limb
(20_b_), is pivotally centred at (21) in the bracket (19) and
normally restrains the turning of the shaft by the weight. There is a
fixed spindle (24) supported on the bracket (23)--which is fixed to the
tank or one of the guide-rods--having centred on it a curved bar or
quadrant (25) running loose on the spindle (24) and having a crank arm
(26) to which is connected one end of a rod (27) which, at the other end,
is connected to the arm (28) of the escapement. The quadrant bears at
both extremities against the flat bar (29) when the bell (22) is
sufficiently raised. The bar (29) extends above the bell and carries an
arm (30) on which is a finger (30_a_). There is fixed on the shaft
(18) a wheel (31), with diagonal divisions or ways extending from side to
side of its rim, and stop-pins (32) on one side at each division. A
clutch prevents the rotation of the wheel during winding up.

[Illustration: FIG. 46.--THE "A" GENERATOR OF FRED K. BRABY AND CO.,
LTD.]

(2) Automatic; water-to-carbide; contact, superposed trays.

The type "B" generator made by this firm comprises an equalising bell
gasholder, a crescent-shaped feed water-tank placed on one side of the
gasholder, and mechanism for controlling a tap on the pipe by which the
feed water passes to a washer whence it overflows through a seal into a
horizontal generating chamber containing cells packed with carbide. The
mechanism controlling the water feed embodies the curved bar (25),
connecting-rod (27) and flat guide-bar (29) as used for controlling the
carbide feed in the "A" type of generator (Fig. 46). When the bell
descends water is fed into the washer, and the water-level of the seal is
thus automatically maintained. The gas evolved passes through a pipe,
connecting the seal on the top of the generating chamber with the washer,
into the gasholder. Plants of large size have two generating chambers
with connexions to a single washer.

_Maker:_ THE DARGUE ACETYLENE GAS CO., 57 GREY STREET, NEWCASTLE-ON-
TYNE.

_Type:_ Automatic; water-to-carbide; "drawer."

The "Dargue" acetylene generator made by this firm comprises an
equalising bell gasholder _B_ floating in a water-tank _A_,
which is deeper than is necessary to submerge the bell of the gasholder.
In the lower part of this tank are placed two or more horizontal
generating chambers which receive carbide-containing trays divided by
partitions into a number of compartments which are half filled with
carbide. Water is supplied from the gasholder tank through the tap
_E_ and pipe _F_ to the generating chambers in turn. It rises
in the latter and floods the first compartment containing carbide before
gaining access to the second, and so on throughout the series of
compartments. As soon as the carbide in the first generating chamber is
exhausted, the water overflows from it through the pipe with by-pass tap
_J_ to the second generating chamber. The taps _G_ and _H_
serve to disconnect one of the generating chambers from the water-supply
during recharging or while another chamber is in action. The gas evolved
passes from each generating chamber through a pipe _L_, terminating
in the dip-pipe _M_, which is provided with a baffle-plate having
very small perforations by which the stream of gas is broken up, thereby
subjecting it to thorough washing by the upper layers of water in the
gasholder tank. The washed gas, which thus enters the gasholder, passes
from it through the pipe _N_ with main cock _R_ to the service-
pipes. The water-supply to the generator is controlled through the tap
_E_, which is operated by a chain connected to an arm attached to
the bell of the gasholder.

The water in the gasholder tank is accordingly made to serve for the
supply of the generating chambers, for the washing of the gas, and as a
jacket to the generating chambers. The heat evolved by the decomposition
of the carbide in the latter creates a circulation of the water, ensuring
thereby thorough mixing of the fresh water, which is added from time to
time to replace that removed for the decomposition of the carbide, with
the water already in the tank. Thus the impurities acquired by the water
from the washing of the gas do not accumulate in it to such an extent as
to render it necessary to run off the whole of the water and refill,
except at long intervals. A purifier, ordinarily charged with puratylene,
is inserted in many cases after the main cock _R_. The same firm
makes an automatic generator on somewhat similar lines, specially
designed for use in autogenous welding, the smaller sizes of which are
readily portable.

[Illustration: FIG. 47.--"DARGUE" GENERATOR.]

_Maker_: J. AND J. DRUMMOND, 162 MARKET STREET, ABERDEEN.

_Type_: Automatic; water-to-carbide; contact.

The generating plant made by this firm comprises two or more generating
vessels _B_ in which carbide is contained in removable cases
perforated at different levels. Water is supplied to these generating
vessels, entering them at the bottom, from an elevated tank _A_
through a pipe _C_, in which is a tap _F_ connected by a lever
and chain _L_ with the bell _G_ of the equalising gasholder
_H_, into which the evolved gas passes. The lever of the tap
_F_ is counter-weighted so that when the bell _G_ descends the
tap is opened, and when the bell rises the tap is closed. The gas passes
from the generating chambers _B_ through the pipe _D_ to the
washer-cooler _E_ and thence to the gasholder. From the latter it
passes through the dry purifier _J_ to the service-pipe. The
gasholder bell is sealed in oil contained in an annular tank instead of
in the usual single-walled tank containing water. The purifying material
ordinarily supplied is puratylene. The apparatus is also made to a large
extent in a compact form specially for use on board ships.

[Illustration: FIG. 48.--J. AND J. DRUMMOND'S GENERATING PLANT.]

_Agents_: FITTINGS, LTD., 112 VICTORIA STREET, S.W.

_Type_: Automatic; carbide-to-water.

The "Westminster" generator supplied by this firm is the "Davis"
generator described in the section of the United States. The rights for
the sale of this generator in Great Britain are held by this firm.

_Maker_: LOCKERBIE AND WILKINSON, TIPTON, STAFFS.

_Type_: (1) Automatic; water-to-carbide; contact, superposed trays.

The "Thorscar" generator of this firm comprises an equalising gasholder,
the gas-space of the bell _B_ of which is reduced by conical upper
walls. When the bell descends and this lining enters the water in the
tank _A_ the displacement of water is increased and its level raised
until it comes above the mouths of the pipes _E_, through which a
portion then flows to the generators _D_. The evolution of the gas
in the latter causes the bell to rise and the conical lining to be lifted
out of the water, the level of which thereupon falls below the mouths of
the pipes _E_ in consequence of the reduced displacement of the
bell. The supply of water to the generators is thus cut off until the
bell again falls and the level of the water in the tank is raised above
the mouths of the pipes _E_. The generating chambers _D_ are
provided with movable cages _F_ in which the carbide is arranged on
trays. The gas evolved travels through a scrubbing-box _G_
containing charcoal, and the pipe _J_ with drainage-pipe _P_ to
the water-seal or washer _K_ inside the holder, into which it then
passes. The outlet-pipe for gas from the holder leads through the
condensing coil _L_ immersed in the water in the tank to the
condensed water-trap _N_, and thence by the tap _Q_ to the
supply-pipe. The generating chambers are water-jacketed and provided with
gauge-glasses _H_ to indicate when recharging is necessary, and also
with sludge-cocks _M_. The object of the displacement cone in the
upper part of the bell is to obtain automatic feed of water to the
carbide without the use of cocks or movable parts. There is a funnel-
shaped indicator in front of the tank for regulating the height of water
to a fixed level, and also an independent purifier, the purifying
material or which is supplied under the proprietary name of "Thorlite."

[Illustration: FIG. 49.--"THORSCAR" GENERATOR.]

(2) Non-automatic; water-to-carbide; "drawer."

This generating plant, the "Thorlite," comprises a water-tank _A_
from which water is admitted to the drawer generating chambers _B_,
one of which may be recharged while the other is in operation. The gas
evolved passes through a seal _C_ to the gasholder _D_, whence
it issues as required for use through the purifier _E_ to the
supply-pipe. For the larger sixes a vertical generating chamber is used.
The purifier and purifying material are the same as for the automatic
plant of the same firm.

[Illustration: FIG. 50.--"THORLITE" GENERATING PLANT.]

_Maker_: THE MANCHESTER ACETYLENE GAS CO., LTD., ACRE WORKS,
CLAYTON, MANCHESTER.

_Type_: Automatic; water-to-carbide; "drawer."

The plant made by this firm comprises an equalising gasholder _A_
from the tank of which water is supplied to generating cylinders _B_
placed at the side of the tank, the number of which varies with the
capacity of the plant. The cylinders receive tray carbide-containers
divided into compartments perforated at different levels so that they are
flooded in turn by the inflowing water. A weight _C_ carried by a
chain _D_ from one end of a lever _E_ pivoted to the framing of
the gasholder is supported by the bell of the gasholder when the latter
rises; but when the holder falls the weight _C_, coming upon the
lever _E_, raises the rod _F_, which thereupon opens the valve
_G_, which then allows water to flow from the gasholder tank through
the pipe _H_ to one of the generating cylinders. When the carbide in
the first cylinder is exhausted, the water passes on to a second. One
generating cylinder may be recharged while another is in action. The
rising of the holder, due to the evolved gas, causes the bell to support
the weight _C_ and thus closes the water supply-valve _G_. The
gas evolved passes through vertical condensers _J_ into washing-
boxes _K_, which are placed within the tank. The gas issues from the
washing-boxes into the gasholder bell, whence it is withdrawn through the
pipe _L_ which leads to the purifier. Puratylene is the purifying
material ordinarily supplied by this firm.

[Illustration: FIG. 51.--GENERATING PLANT OF THE MANCHESTER ACETYLENE GAS
CO., LTD.]

_Maker:_ R,. J. MOSS AND SONS, 98 SNOW HILL, BIRMINGHAM.

_Type:_ (1) Automatic; water-to-carbide; superposed trays.

The "Moss" generator, "Type A," made by this firm comprises an equalising
gasholder, four, three, or two generating chambers, and an intermediate
water-controlling chamber. Each generating chamber consists of a frame in
which are arranged about a central tube trays half filled with carbide,
having water inlet-holes at several different levels, and each divided
into two compartments. Over this frame is put a bell-shaped cover or cap,
and the whole is placed in an outer tank or bucket, in the upper part of
which is a water inlet-orifice. The water entering by this orifice passes
down the outside of the bell, forming a water-seal, and rises within the
bell to the perforations in the carbide trays from the lowest upwards,
and so reaches the carbide in successive layers until the whole has been
exhausted. The gas evolved passes through the central tube to a water-
seal and condensing tank, through which it escapes to the controlling
chamber, which consists of a small water displacement chamber, the gas
outlet of which is connected to the equalising gasholder. The bell of the
equalising gasholder is weighted or balanced so that when it rises to a
certain point the pressure is increased to a slight extent and
consequently the level of the water in the displacement controlling
chamber is lowered. In this chamber is a pipe perforated at about the
water-level, so that when the level is lowered through the increased
pressure thrown by the rising gasholder the water is below the
perforations and cannot enter the pipe. The pipe leads to the water
inlet-orifices of the generating tanks and when the equalising gasholder
falls, and so reduces the pressure within the controlling chamber, the
water in the latter rises and flows through the pipe to the generating
tanks. The water supplied to the carbide is thus under the dual control
of the controlling chamber and of the differential pressure within the
generating tank. The four generators are coupled so that they come into
action in succession automatically, and their order of operation is
naturally reversed after each recharging. An air-cock is provided in the
crown of the bell of each generator and, in case there should be need of
examination when charged, cocks are provided in other parts of the
apparatus for withdrawing water. There is a sludge-cock on each
generator. The gas passes from the equalising gasholder through a
purifier, for which the material ordinarily supplied is puratylene.

[Illustration: FIG. 52.--"MOSS TYPE A" GENERATOR.]

The "Moss Type B" generator is smaller and more compact than "Type A." It
has ordinarily only two generating chambers, and the displacement water
controlling chamber is replaced by a bell governor, the bell of which is
balanced through a lever and chains by a weight suspended over the bell
of the equalising gasholder, which on rising supports this counter-weight
and so allows the governor bell to fall, thereby cutting off the flow of
water to the generating chambers.

[Illustration: FIG 53.--"MOSS TYPE B" GENERATOR.]

The "Moss Type C" generator is smaller than either "Type A" or "B," and
contains only one generating chamber, which is suspended in a pocket in
the crown of the equalising gasholder. Water enters through a hole near
the top of the bucket of the generating chamber, when it descends with
the holder through the withdrawal of gas from the latter.

[Illustration: FIG 54.--"MOSS TYPE C" GENERATOR.]

(2) Semi-automatic; water-to-carbide; superposed trays.

The "Moss Semi-Non-Auto" generating plant resembles the automatic plant
described above, but a storage gasholder capable of holding the gas
evolved from one charging of the whole of the generating chambers is
provided in place of the equalising gasholder, and the generation of gas
proceeds continuously at a slow rate.

The original form of the "Acetylite" generator (_vide infra_)
adapted for lantern use is also obtainable of R. J. Moss and Sons.

_Maker:_ WM. MOYES AND SONS, 115 BOTHWELL STREET, GLASGOW.

_Type:_ Automatic; carbide-to-water.
The "Acetylite" generator made by this firm consists of an equalising
gasholder and one or more generating tanks placed alongside it. On the
top of each generating tank is mounted a chamber, with conical base,
charged with granulated carbide 1/8 to 1/2 inch in size. There is an
opening at the bottom of the conical base through which passes a rod with
conical head, which, when the rod is lowered, closes the opening. The rod
is raised and lowered through levers by the rise and fall of the bell of
the equalising gasholder, which, when it has risen above a certain point,
supports a counter-weight, the pull of which on the lever keeps the
conical feed-valve open. The gas evolved in the generating tanks passes
through a condensing chamber situated at the base of the tank into the
equalising gasholder and so automatically controls the feed of carbide
and the evolution of gas according to the rate of withdrawal of the gas
from the holder to the service-pipes. The water in the gasholder tank
acts as a scrubbing medium to the gas. The generating tanks are provided
with sludge-cocks and a tap for drawing off condensed water. The gas
passes from the equalising gasholder, through a purifier and dryer
charged with heratol or other purifying material to the service-pipes.
The original form of the "Acetylite" generator is shown in elevation and
vertical section in Fig. 55. Wm. Moyes and Sons now make it also with a
detached equalising gasholder connected with the generator by a pipe in
which is inserted a lever cock actuated automatically through a lever and
cords by a weight above the bell of the gasholder. Some other changes
have been made with a view to securing constancy of action over long
periods and uniformity of pressure. In this form the apparatus is also
made provided with a clock-work mechanism for the supply of lighthouses,
in which the light is flashed on periodically. The flasher is operated
through a pilot jet, which serves to ignite the gas at the burners when
the supply is turned on to them at the prescribed intervals by the clock-
work mechanism.

[Illustration: FIG. 55.--"ACETYLITE" GENERATOR.]

_Maker_: THE PHOS CO., 205 AND 207 BALLS POND ROAD, LONDON, N.
_Type_: Non-automatic; water-to-carbide; drip.

The type "E" generator made by this firm consists of a generating chamber
placed below a water chamber having an opening with cap _E_ for
refilling. The generating chamber in closed by a door _B_, with
rubber washer _C_, held in position by the rod _A_, the ends of
which pass into slots, and the screw _A'_. The movable carbide
chamber _D_ has its upper perforated part half filled with carbide,
which is pressed upwards by a spring _D'_. The carbide chamber when
filled is placed in the generating chamber, which is closed, and the
lever _F_ of one of the taps _F'_ is turned from "off" to "on,"
whereupon water drips from the tank on to the carbide. The evolution of
gas is stopped by reversing the lever of the tap. The second tap is
provided for use when the evolution of gas, through the water-supply from
the first tap, has been stopped and it is desired to start the apparatus
without waiting for water from the first tap to soak through a layer of
spent carbide. The two taps are not intended for concurrent use. The
evolved gas passes through a purifier containing any suitable purifying
material to the pipes leading to the burners.

[Illustration: FIG. 56.--"PHOS TYPE E" GENERATOR.]

_Maker:_ ROSCO ACETYLENE COMPANY, BELFAST.

_Type:_ Non-automatic; carbide-to-water

The "Rosco" generating plant made by this firm comprises a generating
tank _A_ which is filled with water to a given level by means of the
funnel-mouthed pipe _B_ and the overflow _O_. On the top of the
water-sealed lid of the generating tank is mounted the carbide feed-valve
_L_, which consists of a hollow plug-tap with handle _M_. When
the handle _M_ is turned upwards the hollow of the tap can be filled
from the top of the barrel with carbide. On giving the tap a third of a
turn the hollow of the plug is cut off from the outer air and is opened
to the generating tank so that the carbide contained in it is discharged
over a distributor _E_ on to the tray _N_ in the water in the
generating tank. The gas evolved passes through the scrubber and seal-pot
_J_ to the storage gasholder _Q_. From the latter the gas
passes through the dry purifier _T_ to the service-pipe. A sludge-
cock _P_ is provided at the bottom of the generating tank and is
stated to be available for use while generation of gas is proceeding. The
purifying material ordinarily supplied is "Roscoline."

[Illustration: FIG. 57.--"ROSCO" GENERATING PLANT.]

_Maker_: THE RURAL DISTRICTS GAS LIGHT CO., 28 VICTORIA STREET, S.W.

_Type_: Automatic; water-to-carbide; contact, superposed trays.

The "Signal-Arm" generating apparatus made by this firm comprises a bell
gasholder _A_, from the tank _B_ of which water is supplied
through a swivelled pipe _C_ to a generating chamber _D_. One
end of the swivelled pipe is provided with a delivery nozzle, the other
end is closed and counter-weighted, so that normally the open end of the
pipe is raised above the level of the water in the tank. A tappet
_E_ on the bell of the gasholder comes into contact with, and
depresses, the open end of the swivelled pipe when the bell falls below a
certain point. As soon as the open end of the swivelled pipe has thus
been lowered below the level of the water in the tank, water flows
through it into the funnel-shaped mouth _F_ of a pipe leading to the
bottom of the generating chamber. The latter is filled with cages
containing carbide, which is attacked by the water rising in the chamber.
The gas evolved passing into and raising the bell of the gasholder causes
the open end of the swivelled pipe to rise, through the weight of the
counterpoise _G_, above the level of the water in the tank and so
cuts off the supply of water to the generating chamber until the bell
again descends and depresses the swivelled pipe. The tappet on the bell
also displaces a cap _H_ which covers the funnel-shaped mouth of the
pipe leading to the generating chamber, which cap, except when the
swivelled supply-pipe is being brought into play, prevents any extraneous
moisture or other matter entering the mouth of the funnel. Between the
generating chamber and the gasholder is a three-way cock _J_ in the
gas connexion, which, when the gasholder is shut off from the generator,
brings the latter into communication with a vent-pipe _K_ leading to
the open. The gas passes from the holder to a chamber _L_ under
grids packed with purifying material, through which it passes to the
outlet of the purifier and thence to the service-pipe. Either heratol or
chloride of lime is used in the purifier, the lid of which, like the
cover of the generator, is water-sealed.

[Illustration: FIG. 58.--"SIGNAL-ARM" GENERATING PLANT.]

_Maker_: ST. JAMES' ILLUMINATING CO., LTD., 3 VICTORIA STREET,
LONDON, S.W.

_Type_: (1) Automatic; water-to-carbide; contact, superposed trays.

This plant consists of the generators _A_, the washer _B_, the
equalising gasholder _C_, the purifier _D_, and the water-tank
_E_. The carbide is arranged in baskets in the generators to which
water is supplied from the cistern _E_ through the pipe _F_.
The supply is controlled by means of the valve _H_, which is
actuated through the rod _G_ by the rise and fall of the gasholder
_C_. Gas travels from the gasholder through the purifier _D_ to
the service-pipe. The purifier is packed with heratol resting on a layer
of pumice. The washer _B_ contains a grid, the object of which is to
distribute the stream of gas through the water. There is a syphon-pot
_J_ for the reception of condensed moisture. Taps _K_ are
provided for shutting off the supply of water from the generators during;
recharging, and there is an overflow connexion _L_ for conveying the
water to the second generator as soon as the first is exhausted. There is
a sludge-cock _M_ at the base of each generator.

(2) Non-automatic; water-to-carbide; contact, superposed trays.

This resembles the preceding plant except that the supply of water from
the cistern to the generators takes place directly through the pipe
_N_ (shown in dotted lines in the diagram) and is controlled by hand
through the taps _K_. The automatic control-valve _H_ and the
rod _G_ are omitted. The gasholder _C_ is increased in size so
that it becomes a storage holder capable of containing the whole of the
gas evolved from one charging.

[Illustration: FIG. 59.--GENERATING PLANT OF THE ST. JAMES' ILLUMINATING
CO., LTD. (SECTIONAL ELEVATION AND PLAN.)]

_Maker_: THE STANDARD ACETYLENE CO., 123 VICTORIA STREET, LONDON,
S.W.

_Type_: (1) Non-automatic; carbide-to-water.

This plant comprises the generator _A_, the washer _B_, the
storage gasholder _C_, and the purifier _D_. The generator is
first filled with water to the crown of the cover, and carbide is then
thrown into the water by hand through the gas-tight lock, which is opened
and closed as required by the horizontal handle _P_. A cast-iron
grid prevents the lumps of carbide falling into the sludge in the conical
base of the generator. At the base of the cone is a sludge-valve
_G_. The gas passes from the generator through the pipe _H_
into the washer _B_, and after bubbling through the water therein
goes by way of the pipe _K_ into the gasholder _C_. The syphon-
pot _E_ is provided for the reception of condensed moisture, which
is removed from time to time by the pump _M_. From the gasholder the
gas flows through the valve _R_ to the purifier _D_, whence it
passes to the service-pipes. The purifier is charged with material
supplied under the proprietary name of "Standard."

[Illustration: FIG. 60.--CARBIDE-TO-WATER GENERATING PLANT OF THE STANDARD
ACETYLENE CO.]

(2) Automatic; water-to-carbide; contact, superposed trays.

This plant comprises the generators _A_, the washer _B_, the
equalising gasholder _C_, the purifier _D_, and the water-tank
_E_. The carbide is arranged on a series of wire trays in each
generator, to which water is supplied from the water-tank _E_
through the pipe _Y_ and the control-tap _U_. The gas passes
through the pipes _H_ to the washer _B_ and thence to the
holder _C_. The supply of water to the generators is controlled by
the tap _U_ which is actuated by the rise and fall of the gasholder
bell through the rod _F_. The gas passes, as in the non-automatic
plant, through a purifier _D_ to the service-pipes. Taps _W_
are provided for cutting off the flow of water to either of the
generators during recharging and an overflow pipe _h_ serves to
convey the water to the second generator as soon as the carbide in the
first is exhausted. A sludge-cook _G_ is put at the base of each
generator.

[Illustration: FIG. 61.--AUTOMATIC, WATER-TO-CARBIDE GENERATING PLANT OF
THE STANDARD ACETYLENE CO.]

(3) Non-automatic; water-to-carbide; contact, superposed-trays.

This apparatus resembles the preceding except that the supply of water to
the generators is controlled by hand through the taps _W_, the
control valve _U_ being omitted, and the gasholder _C_ being a
storage holder of sufficient dimensions to contain the whole of the
acetylene evolved from one charging.

_Maker_: THORN AND HODDLE ACETYLENE CO., 151 VICTORIA STREET, S.W.

_Type_: Automatic; water-to-carbide; "drawer."

The "Incanto" generating plant made by this firm consists of a rising
bell gasholder which acts mainly on an equaliser. The fall of the bell
depresses a ball valve immersed in the tank, and so allows water to flow
from the tank past an outside tap, which is closed only during
recharging, to a generating chamber. The generating chamber is horizontal
and is fixed in the base of the tank, so that its outer case is
surrounded by the water in the tank, with the object of keeping it cool.
The charge of carbide is placed in a partitioned container, and is
gradually attacked on the flooding principle by the water which enters
from the gasholder tank when the ball valve is depressed. The gas evolved
passes from the generating chamber by a pipe which extends above the
level of the water in the tank, and is then bent down so that its end
dips several inches below the level of the water. The gas issuing from
the end of the pipe is thus washed by the water in the gasholder tank.
From the gasholder the gas is taken off as required for use by a pipe,
the mouth of which is just below the crown of the holder. There is a lip
in the upper edge of the gasholder tank into which water is poured from
time to time to replace that consumed in the generation of the gas. There
are from one to three generating chambers in each apparatus according to
its size. The purifier is independent, and a purifying mixture under the
proprietary name of "Curazo" is supplied for use in it.

[Illustration: FIG. 62.--"INCANTO" GENERATOR.]

_Maker:_ WELDREN AND BLERIOT, 54 LONG ACRE, LONDON, W.C.

_Type:_ Automatic; contact.

This firm supplies the "Acetylithe" apparatus (_see_ Belgium).

INDEX

Absorbed acetylene,
Acagine,
Accidents, responsibility for,
Acetone, effect of, on acetylene,
solution of acetylene in,
Acetylene-copper,
Acetylene-oil-gas,
Acetylene Association (Austrian)--regulations as to carbide,
Acetylene Association (British)--analysis of carbide,
generator rules,
pressure gauges,
purification rules,
Acetylene Association (German)--analysis of carbide,
holders,
generator rules,
standard carbide,
Acetylene tetrachloride, production of,
Ackermann burner,
Advantages of acetylene, general,
hygienic,
intrinsic,
pecuniary,
"After generation,"
Air, admission of, to burners,
and acetylene, ignition temperature of,
composition of,
dilution of acetylene with, before combustion,
effect of acetylene lighting on,
coal-gas lighting on,
on illuminating power of acetylene,
paraffin lighting on,
in acetylene,
in flames, effect of,
in generators, danger of,
objections to,
in incandescent acetylene,
in service-pipes,
proportion of, rendering acetylene explosive,
removing, from pipes,
specific gravity of,
sterilised by flames,
Air-gas,
and acetylene, comparison between,
and carburetted acetylene, comparison between,

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