and all have complicated; reactions of their own. In the reds are rosanilines, toluidine xylidine, &c.; in the blues–phenyl-rosanilines, diphenylamine, toluidine, aldehyde, &c.; violets–rosaniline, mauve, phenyl, ethyl, methyl, &c.; greens–iodine, aniline, leucaniline, chrysotoluidine, aldehyde, toluidine, methyl-anilinine, &c.; yellows and orange–leucaniline, phenylamine, &c.; browns–chrysotoluidine, &c.; blacks–aniline, toluidine, &c.
To take the rosanilines as an instance of the rest.
Aniline red, magenta, azaleine, rubine, solferino, fuchsine, chryaline, roseine, erythrobenzine, and others, are colouring matters in this group which are salts of rosaniline, and which are all recognised in commerce.
The base rosaniline is known chemically by the formula C_{20}H_{l9}N_{3}, and is prepared by heating a mixture of magenta aniline, toluidine, and pseudotoluidine, with arsenic acid and other oxidising agents. It is important that water should be used in such quantities as to prevent the solution of arsenic acid from depositing crystals on cooling. Unless carefully crystallised rosaniline will contain a slight proportion of the arseniate, and when articles of clothing are dyed with the salt, it is likely to produce an inflammatory condition of skin, when worn. Some years ago there was a great outcry against hose and other articles dyed with aniline dyes, owing to the bad effects which were produced, and this has no doubt proved very prejudicial to aniline dyes as a whole.
Again, the base known as mauve, or mauveine, has a composition shown by the formula C_{27}H_{24}N_{4}. It is produced from the sulphate of aniline by mixing it with a cold saturated solution of bichromate of potash, and allowing the mixture to stand for ten or twelve hours. A blue-black precipitate is then formed, which, after undergoing a process of purification, is dissolved in alcohol and evaporated to dryness. A metallic-looking powder is then obtained, which constitutes this all-important base. Mauve forms with acids a series of well-defined salts and is capable of expelling ammonia from its combinations. Mauve was the first aniline dye which was produced on a large scale, this being accomplished by Perkin in 1856.
The substance known as carbolic acid is so useful a product of a piece of coal that a description of the method of its production must necessarily have a place here. It is one of the most powerful antiseptic agents with which we are acquainted, and has strong anaesthetic qualities. Some useful dyes are also obtained from it. It is obtained in quantities from coal-tar, that portion of the distillate known as the light oils being its immediate source. The tar oil is mixed with a solution of caustic soda, and the mixture is violently agitated. This results in the caustic soda dissolving out the carbolic acid, whilst the undissolved oils collect upon the surface, allowing the alkaline solution to be drawn from beneath. The soda in the solution is then neutralised by the addition of a suitable quantity of sulphuric acid, and the salt so formed sinks while the carbolic acid rises to the surface.
Purification of the product is afterwards carried out by a process of fractional distillation. There are various other methods of preparing carbolic acid.
Carbolic acid is known chemically as C_{6}H_{5}(HO). When pure it appears as colourless needle-like crystals, and is exceedingly poisonous. It has been used with marked success in staying the course of disease, such as cholera and cattle plague. It is of a very volatile nature, and its efficacy lies in its power of destroying germs as they float in the atmosphere. Modern science tells us that all diseases have their origin in certain germs which are everywhere present and which seek only a suitable _nidus_ in which to propagate and flourish. Unlike mere deodorisers which simply remove noxious gases or odours; unlike disinfectants which prevent the spread of infection, carbolic acid strikes at the very root and origin of disease by oxidising and consuming the germs which breed it. So powerful is it that one part in five thousand parts of flour paste, blood, &c., will for months prevent fermentation and putrefaction, whilst a little of its vapour in the atmosphere will preserve meat, as well as prevent it from becoming fly-blown. Although it has, in certain impure states, a slightly disagreeable odour, this is never such as to be in any way harmful, whilst on the other hand it is said to act as a tonic to those connected with its preparation and use.
The new artificial colouring matters which are continually being brought into the market, testify to the fact that, even with the many beautiful tints and hues which have been discovered, finality and perfection have not yet been reached. A good deal of popular prejudice has arisen against certain aniline dyes on account of their inferiority to many of the old dye-stuffs in respect to their fastness, but in recent years the manufacture of many which were under this disadvantage of looseness of dye, has entirely ceased, whilst others have been introduced which are quite as fast, and sometimes even faster than the natural dyes.
It is convenient to express the constituents of coal-tar, and the distillates of those constituents, in the form of a genealogical chart, and thus, by way of conclusion, summarise the results which we have noticed.
COAL.
|
.———-+———–+—-+——————-+——–+—-. | | | | | |
Water House-gas Coal-tar Ammoniacal Coke | | liquor |
.———+——-+———+———. | Sulphur | | | | | | (sulphurreted First Second Heavy Anthracene Pitch | hydrogen: light light oils (green | sulphurous oils oils (creosote oils) | acid: oil | (crude oils) | | of vitriol) .—-+—-. naphtha) | Anthracene | | | | | | |
Ammoniacal Benzene | | Alizarin or | liquor toluene,| | dyer’s madder | &c. | | |
| | |
| | Sulphuric acid=Carbonate of=Hydrochloric | | | ammonia acid | | | (smelling
| | | salts)
| | |
| | Lime=Sulphate of Lime=Chloride of | | | ammonia | ammonia (sal | | | | ammoniac) | | | |
| | .—-+—-. .—-+—-. | | | | | |
| | Ammonia Sulphate Ammonia Chloride | | of lime of lime. | | (Plaster of Paris)
| |
| .–+—–+———-.
| | | |
| Crude Carbolic Naphthalin | Creosote acid
|
.————–+—+–+——-+——–+———–. | | | | |
Benzene=Nitric Acid Toluene Nylene Artificial Burning | turpentine oils
Nitrobenzene= } Iron filings oil (solvent (Essence de | } and acetic acid naphtha) mirbane) |
|
Aniline=Various reagents
|
Aniline dyes
INDEX.
A.
Accidents, causes of mining
“Age of _Acrogens_”
_Alethopteris_
Alizarin
American coal-fields
Ammoniacal liquor
Aniline
Aniline dyes
Aniline oil, commercial
Aniline salt
Aniline “tailings”
Anthracene
Anthracite
Artificial turpentine oil
Asphalt
Australian coals
_Aviculopecten_
B.
Bechamp’s process
Benzene
Bind
Bitumen in Trinidad
“Blower” a
Boghead coal
Bog-oak
Boring diamonds
Borrowdale graphite mine
Bovey Tracey lignite
British coal-fields
British North-American coal-measures Briquettes
C.
_Calamites_, extinct horsetails
Carbolic acid
Carboniferous formation, the
_Cardiocarpum_, fossil fruit
Carelessness of miners
Causes of earth-movements
Changes of level
Charcoal as a disinfectant
Chemistry of a gas-flame
Chinese coals
Clanny’s safety-lamp
Clayton’s experiments with gas
Clay, regularity in deposition of
Club-mosses, great height of fossil Coal-dust, danger from
Coal formed in large lakes or closed seas Coal formation, geological position of
Coal formed by escape of gases
Coal-mine, the
Coal not the result of drifted vegetation Coal-period, climate of
“Coal-pipes”
Coal-plants, classification of
Coal-seam, each, a forest growth
Coals of non-carboniferous age
Coal, vegetable origin of
Coke
“Cole”
“Condensers”
Cones of _Lepidodendra_
Conifers in coal-measures
Current-bedding in sandstone
D.
Davy-lamp
Dangers of benzene
Darwin on the Chonos Archipelago
Diamonds, how made artificially
Disintegration of vegetable substances Disproportion in relative thickness of coal and coal-measures
E.
Early use of coal
Effects of an explosion
Encrinital limestone
_Equiseta_
“Essence de mirbane”
European coal-fields
Evelyn on the use of coal
Experiments illustrating fossilisation
F.
Filling retorts by machinery
Firedamp
Fire, mines on
First light oils
First record of an explosion
Flashing-point of oil
Flooding of pits
Fog and smoke
_Foraminifera_
Fossil ferns
Fructification on fossil-ferns
Furnace, ventilating
G.
Gas, coal
Gasholder, the
Gas, house, constituents of
_Glossopteris_
Graphite
“Green Grease”
H.
Hannay, of Glasgow
Heavy oils
Humboldt’s safety-lamp
Hydraulic Main
I.
Impurities in house-gas
Indian coals
Insertion of rootlets of _stigmaria_ Insufficiency of modern forest growths
Ireland denuded of coal-beds
Iron, supplies of
L.
_Lepidodendra_
_Lepidostrobi_
Lignite
London lit by gas
M.
Mammoth trees
Marco Polo
Marsh gas
Medium oils
Metamorphism of coal by igneous agency Methods of ventilation
Mountain limestone
Murdock’s use of gas
Mussel beds
N.
Napthalin
_Neuropteris_
Newcastle, charters to
Nitro-benzole
O.
Objections to use of coal
Oils from coal and lignite
Oil-wells of America
Olefiant gas
_Orthoceras_
P.
Paraffins
Peat
_Pecopteris_
Pennsylvanian anthracite
Persian fire-worshippers
Pitch
Plumbago
_Polyzoa_
Prejudice against aniline dyes
Prohibitions of the use of coal
Proportions of explosive mixtures
_Psaronius_
“Purifiers”
Pyrites in coal
Q.
Quantity of coal raised in Great Britain
R.
Reptiles of the coal-era
Resemblance of American and British coal-_flora_ Retorts
Roman use of coal
Rosanilines, the
Royal Commission of 1866
S.
Sandstone, how formed
Shales
_Sigillaria_
South American coals
Spores of _lepidodrendron_
Spores, resinous matter in
Spores, inflammability of
Steel-mill
_Sternbergia_
_Stigmaria_
Subsidence throughout coal-era
Surturbrand at Brighton
Sussex iron-works
T.
Tar
Testing pits by the candle
Texas coal
Toluene, discovery of
Torbanehill mineral
Trappers
U.
Underclays
Uses to which coal is put
V.
Vaseline
Vegetation of the coal age
Ventilation of coal-pits
W.
“Washers”
Waste of fuel
Wealden lignite
Westphalian coal-field
Y.
Young’s Paraffin Oil
Z.
Zoroastrians