The Story of a Piece of Coal
Edward A. Martin

Part 3 out of 3

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

| | | | | |
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



Accidents, causes of mining
"Age of _Acrogens_"
American coal-fields
Ammoniacal liquor
Aniline dyes
Aniline oil, commercial
Aniline salt
Aniline "tailings"
Artificial turpentine oil
Australian coals


Bechamp's process
Bitumen in Trinidad
"Blower" a
Boghead coal
Boring diamonds
Borrowdale graphite mine
Bovey Tracey lignite
British coal-fields
British North-American coal-measures


_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-plants, classification of
Coal-seam, each, a forest growth
Coals of non-carboniferous age
Coal, vegetable origin of
Cones of _Lepidodendra_
Conifers in coal-measures
Current-bedding in sandstone


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


Early use of coal
Effects of an explosion
Encrinital limestone
"Essence de mirbane"
European coal-fields
Evelyn on the use of coal
Experiments illustrating fossilisation


Filling retorts by machinery
Fire, mines on
First light oils
First record of an explosion
Flashing-point of oil
Flooding of pits
Fog and smoke
Fossil ferns
Fructification on fossil-ferns
Furnace, ventilating


Gas, coal
Gasholder, the
Gas, house, constituents of
"Green Grease"


Hannay, of Glasgow
Heavy oils
Humboldt's safety-lamp
Hydraulic Main


Impurities in house-gas
Indian coals
Insertion of rootlets of _stigmaria_
Insufficiency of modern forest growths
Ireland denuded of coal-beds
Iron, supplies of


London lit by gas


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


Newcastle, charters to


Objections to use of coal
Oils from coal and lignite
Oil-wells of America
Olefiant gas


Pennsylvanian anthracite
Persian fire-worshippers
Prejudice against aniline dyes
Prohibitions of the use of coal
Proportions of explosive mixtures
Pyrites in coal


Quantity of coal raised in Great Britain


Reptiles of the coal-era
Resemblance of American and British coal-_flora_
Roman use of coal
Rosanilines, the
Royal Commission of 1866


Sandstone, how formed
South American coals
Spores of _lepidodrendron_
Spores, resinous matter in
Spores, inflammability of
Subsidence throughout coal-era
Surturbrand at Brighton
Sussex iron-works


Testing pits by the candle
Texas coal
Toluene, discovery of
Torbanehill mineral


Uses to which coal is put


Vegetation of the coal age
Ventilation of coal-pits


Waste of fuel
Wealden lignite
Westphalian coal-field


Young's Paraffin Oil




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