Book: The Story of a Piece of Coal

E >> Edward A. Martin >> The Story of a Piece of Coal




By distillation of the _heavy oils_, carbolic acid and commercial
_anthracene_ are produced, and by a treatment of the residue, a white and
crystalline substance known as _naphthalin_ (C_{10}H_{8}) is finally
obtained.

Thus, by the continued operation of the chemical process known as
fractional distillation of the immediate products of coal-tar, these
various series of useful oils are prepared.

The treatment is much the same which has resulted in the production of
paraffin oil, to which we have previously referred, and an account of the
production of coal-oils would be very far from satisfactory, which made
no mention of the production of similar commodities by the direct
distillation of shale. Oil-shales, or bituminous shales, exist in all
parts of the world, and may be regarded as mineral matter largely
impregnated by the products of decaying vegetation. They therefore
greatly resemble some coals, and really only differ therefrom in degree,
in the quantity of vegetable matter which they contain. Into the subject
of the various native petroleums which have been found--for these
rock-oils are better known as petroleums--in South America, in Burmah
(Rangoon Oil), at Baku, and the shores of the Caspian, or in the United
States of America, we need not enter, except to note that in all
probability the action of heat on underground bituminous strata of
enormous extent has been the cause of their production, just as on a
smaller scale the action of artificial heat has forced the reluctant
shale to give up its own burden of mineral oil. However, previous to
1847, although native mineral oil had been for some years a recognised
article of commerce, the causes which gave rise to the oil-wells, and the
source, probably a deep-seated one, of the supply of oil, does not appear
to have been well known, or at least was not enquired after. But in that
year Mr Young, a chemist at Manchester, discovered that by distilling
some petroleum, which he obtained from a spring at Riddings in
Derbyshire, he was able to procure a light oil, which he used for burning
in lamps, whilst the heavier product which he also obtained proved a most
useful lubricant for machinery. This naturally distilled oil was soon
found to be similar to that oil which was noticed dripping from the roof
of a coal-mine. Judging that the coal, being under the influence of heat,
was the cause of the production of the oil, Mr Young tested this
conclusion by distilling the coal itself. Success attended his endeavour
thus to procure the oil, and indelibly Young stamped his name upon the
roll of famous men, whose industrial inventions have done so much towards
the accomplishment of the marvellous progress of the present century.
From the distillation he obtained the well-known Young's Paraffin Oil,
and the astonishing developments of the process which have taken place
since he obtained his patent in 1850, for the manufacture of oils and
solid paraffin, must have been a source of great satisfaction to him
before his death, which occurred in 1883.

Cannel coal, Boghead or Bathgate coal, and bituminous shales of various
qualities, have all been requisitioned for the production of oils, and
from these various sources the crude naphthas, which bear a variety of
names according to some peculiarity in their origin, or place of
occurrence, are obtained. Boghead coal, also known as "Torebanehill
mineral," gives Boghead naphtha, while the crude naphtha obtained from
shales is often quoted as shale-oil. In chemical composition these
naphthas are closely related to one another, and by fractional
distillation of them similar series of products are obtained as those we
have already seen as obtained from the crude coal-naphtha of coal-tar.

In the direct distillation of cannel-coal for the production of paraffin,
it is necessary that the perpendicular tubes or retorts into which the
coal is placed be heated only to a certain temperature, which is
considerably lower than that applied when the object is the production of
coal-gas. By this means nearly all the volatile matters pass over in the
form of condensible vapours, and the crude oils are at once formed, from
whence are obtained at different temperatures various volatile ethers,
benzene, and artificial turpentine oil or petroleum spirit. After these,
the well-known safety-burning paraffin oil follows, but it is essential
that the previous three volatile products be completely cleared first,
since, mixed with air, they form highly dangerous explosives. To the fact
that the operation is carried on in the manufactories with great care and
accuracy can only be attributed the comparative rareness of explosions of
the oil used in households.

After paraffin, the heavy lubricating oils are next given off, still
increasing the temperature, and, the residue being in turn subjected to a
very low temperature, the white solid substance known as paraffin, so
much used for making candles, is the result. By a different treatment of
the same residue is produced that wonderful salve for tender skins, cuts,
and burns, known popularly as _vaseline_. Probably no such
widely-advertised remedial substance has so deserved its success as this
universally-used waste product of petroleum.

We have noticed the fact that in order to procure safety-burning oils, it
is absolutely necessary that the more volatile portions be completely
distilled over first. By Act of Parliament a test is applied to all oils
which are intended for purposes of illumination, and the test used
consists of what is known as the flashing-point. Many of the more
volatile ethers, which are highly inflammable, are given off even at
ordinary temperatures, and the application of a light to the oil will
cause the volatile portion to "flash," as it is called. A safety-burning
oil, according to the Act, must not flash under 100 deg. Fahrenheit open
test, and all those portions which flash at a less temperature must be
volatilised off before the residue can be deemed a safe oil. It seems
probable that the flashing-point will sooner or later be raised.

One instance may be cited to show how necessary it is that the native
mineral oils which have been discovered should have this effectual test
applied to them.

When the oil-wells were first discovered in America, the oil was obtained
simply by a process of boring, and the fountain of oil which was bored
into at times was so prolific, that it rushed out with a force which
carried all obstacles before it, and defied all control. In one instance
a column of oil shot into the air to a height of forty feet, and defied
all attempts to keep it under. In order to prevent further accident, all
lights in the immediate neighbourhood were extinguished, the nearest
remaining being at a distance of four hundred feet. But in this crude
naphtha there was, as usual, a quantity of volatile spirit which was
being given off even at the temperature of the surrounding atmosphere.
This soon became ignited, and with an explosion the column of oil was
suddenly converted into a roaring column of fire. The owner of the
property was thrown a distance of twenty feet by the explosion, and soon
afterwards died from the burns which he had received from it. Such an
accident could not now, however, happen. The tapping, stopping, and
regulating of gushing wells can now be more effectually dealt with, and
in the process of refining; the most inflammable portions are separated,
with a result that, as no oil is used in the country which flashes under
100 deg. F. open test, and as our normal temperature is considerably less
than this, there is little to be feared in the way of explosion if the
Act be complied with.

When the results of Mr Young's labours became publicly known, a number of
companies were started with the object of working on the lines laid down
in his patent, and these not only in Great Britain but also in the United
States, whither quantities of cannel coal were shipped from England and
other parts to feed the retorts. In 1860, according to the statistics
furnished, some seventy factories were established in the United States
alone with the object of extracting oil from coal and other mineral
sources, such as bituminous shale, etc. When Young's patent finally
expired, a still greater impetus was given to its production, and the
manufacture would probably have continued to develop were it not that
attention had, two years previously, been forcibly turned to those
discoveries of great stores of natural oil in existence beneath a
comparatively thin crust of earth, and which, when bored into, spouted
out to tremendous heights.

The discovery of these oil-fountains checked for a time the development
of the industry, but with the great production there has apparently been
a greatly increased demand for it, and the British industry once again
appears to thrive, until even bituminous shales have been brought under
requisition for their contribution to the national wealth.

Were it not for the nuisance and difficulty experienced in the proper
cleaning and trimming of lamps, there seems no other reason why mineral
oil should not in turn have superseded the use of gas, even as gas had,
years before, superseded the expensive animal and vegetable oils which
had formerly been in use.

Although this great development in the use of mineral oils has taken
place only within the last thirty years, it must not be thought that
their use is altogether of modern invention. That they were not
altogether unknown in the fifth century before Christ is a matter of
certainty, and at the time when the Persian Empire was at the zenith of
its glory, the fires in the temples of the fire-worshippers were
undoubtedly kept fed by the natural petroleum which the districts around
afforded. It is thought by some that the legend which speaks of the fire
which came down from heaven, and which lit the altars of the
Zoroastrians, may have had its origin in the discovery of a hitherto
unknown petroleum spring. More recently, the remarks of Marco Polo in his
account of his travels in A.D. 1260 and following years, are particularly
interesting as showing that, even then, the use of mineral oil for
various purposes was not altogether unknown. He says that on the north of
Armenia the Greater is "Zorzania, in the confines of which a fountain is
found, from which a liquor like oil flows, and though unprofitable for
the seasoning of meat, yet is very fit for the supplying of lamps, and to
anoint other things; and this natural oil flows constantly, and that in
plenty enough to lade camels."

From this we can infer that the nature of the oil was entirely unknown,
for it was a "liquor like oil," and was also, strange to say,
"unprofitable for the seasoning of meat"! In another place in Armenia,
Marco Polo states that there was a fountain "whence rises oil in such
abundance that a hundred ships might be at once loaded with it. It is not
good for eating, but very fit for fuel, for anointing the camels in
maladies of the skin, and for other purposes; for which reason people
come from a great distance for it, and nothing else is burned in all this
country."

The remedial effects of the oil, when used as an ointment, were thus
early recognised, and the far-famed vaseline of the present day may be
regarded as the lineal descendent, so to speak, of the crude medicinal
agent to which Marco Polo refers.

The term asphalt has been applied to so many and various mixtures, that
one scarcely associates it with natural mineral pitch which is found in
some parts of the world. From time immemorial this compact, bituminous,
resinous mineral has been discovered in masses on the shores of the Dead
Sea, which has in consequence received the well-known title of Lake
Asphaltites. Like the naphthas and petroleums which have been noticed,
this has had its origin in the decomposition of vegetable matter, and
appears to be thrown up in a liquid form by the volcanic energies which,
are still believed to be active in the centre of the lake, and which may
be existent beneath a stratum, or bed, of oil-producing bitumen.

In connection with the formation of this substance, the remarks of Sir
Charles Lyell, the great geologist, may well be quoted, as showing the
transformation of vegetable matter into petroleum, and afterwards into
solid-looking asphalt. At Trinidad is a lake of bitumen which is a mile
and a half in circumference. "The Orinoco has for ages been rolling down
great quantities of woody and vegetable bodies into the surrounding sea,
where, by the influence of currents and eddies, they may be arrested, and
accumulated in particular places. The frequent occurrence of earthquakes
and other indications of volcanic action in those parts, lend countenance
to the opinion that these vegetable substances may have undergone, by the
agency of subterranean fire, those transformations or chemical changes
which produce petroleum; and this may, by the same causes, be forced up
to the surface, where, by exposure to the air, it becomes inspissated,
and forms those different varieties of earth-pitch or asphaltum so
abundant in the island."

It is interesting to note also that it was obtained, at an ancient
period, from the oil-fountains of Is, and that it was put to considerable
use in the embalming of the bodies of the Egyptians. It appears, too, to
have been employed in the construction of the walls of Babylon, and thus
from very early times these wonderful products and results of decayed
vegetation have been brought into use for the service of man.

Aniline has been previously referred (p. 135) to as having been prepared
from nitro-benzole, or _essence de mirbane_, and its preparation, by
treating this substance with iron-filings and acetic acid, was one of the
early triumphs of the chemists who undertook the search after the unknown
contained in gas-tar. It had previously been obtained from oils distilled
from bones. The importance of the substance lies in the fact that, by the
action of various chemical reagents, a series of colouring matters of
very great richness are formed, and these are the well-known _aniline
dyes_.

As early as 1836, it was discovered that aniline, when heated with
chloride of lime, acquired a beautiful blue tint. This discovery led to
no immediate practical result, and it was not until twenty-one years
after that a further discovery was made, which may indeed be said to have
achieved a world-wide reputation. It was found that, by adding bichromate
of potash to a solution of aniline and sulphuric acid, a powder was
obtained from which the dye was afterwards extracted, which is known as
_mauve_. Since that time dyes in all shades and colours have been
obtained from the same source. _Magenta_ was the next dye to make its
appearance, and in the fickle history of fashion, probably no colours
have had such extraordinary runs of popularity as those of mauve and
magenta. Every conceivable colour was obtained in due course from the
same source, and chemists began to suspect that, in the course of time,
the colouring matter of dyer's madder, which was known as _alizarin_,
would also be obtained therefrom. Hitherto this had been obtained from
the root of the madder-plant, but by dint of careful and well-reasoned
research, it was obtained by Dr Groebe, from a solid crystalline coal-tar
product, known as _anthracene_, (C_{12}H_{14}). This artificial alizarin
yields colours which are purer than those of natural madder, and being
derived from what was originally regarded as a waste product, its cost of
production is considerably cheaper.

We have endeavoured thus far to deal with (1) gas, and (2) tar, the two
principal products in the distillation of coal. We have yet to say a few
words concerning the useful ammoniacal liquor, and the final residue in
the retorts, _i.e._, coke.

The ammoniacal liquor which has been passing over during distillation of
the coal, and which has been collecting in the hydraulic main and in
other parts of the gas-making apparatus, is set aside to be treated to a
variety of chemical reactions, in order to wrench from it its useful
constituents. Amongst these, of course, _ammonia_ stands in the first
rank, the others being comparatively unimportant. In order to obtain
this, the liquor is first of all neutralised by being treated with a
quantity of acid, which converts the principal constituent of the liquor,
viz., carbonate of ammonia (smelling salts), into either sulphate of
ammonia, or chloride of ammonia, familiarly known as sal-ammoniac,
according as sulphuric acid or hydrochloric acid is the acid used. Thus
carbonate of ammonia with sulphuric acid will give sulphate of ammonia,
but carbonate of ammonia with hydrochloric acid will give sal-ammoniac
(chloride of ammonia). By a further treatment of these with lime, or, as
it is chemically known, oxide of calcium, ammonia is set free, whilst
chloride of lime (the well-known disinfectant), or sulphate of lime
(gypsum, or "plaster of Paris" ), is the result.

Thus:

Sulphate of ammonia + lime = plaster of Paris + ammonia.

or,

Sal-ammoniac + lime = chloride of lime + ammonia.

Ammonia itself is a most powerful gas, and acts rapidly upon the eyes. It
has a stimulating effect upon the nerves. It is not a chemical element,
being composed of three parts of hydrogen by weight to one of nitrogen,
both of which elements alone are very harmless, and, the latter indeed,
very necessary to human life. Ammonia is fatal to life, producing great
irritation of the lungs.

It has also been called "hartshorn," being obtained by destructive
distillation of horn and bone. The name "ammonia" is said to have been
derived from the fact that it was first obtained by the Arabs near the
temple of Jupiter Ammon, in Lybia, North Africa, from the excrement of
camels, in the form of sal-ammoniac. There are always traces of it in the
atmosphere, especially in the vicinity of large towns and manufactories
where large quantities of coal are burned.

Coke, if properly prepared, should consist of pure carbon. Good coal
should yield as much as 80 per cent. of coke, but owing to the
unsatisfactory manner of its production, this proportion is seldom
yielded, whilst the coke which is familiar to householders, being the
residue left in the retorts after gas-making, usually contains so large a
proportion of sulphur as to make its combustion almost offensive. No
doubt the result of its unsatisfactory preparation has been that it has
failed to make its way into households as it should have done, but there
is also another objection to its use, namely, the fact that, owing to the
quantity of oxygen required in its combustion, it gives rise to feelings
of suffocation where insufficient ventilation of the room is provided.

Large quantities of coke are, however, consumed in the feeding of furnace
fires, and in the heating of boilers of locomotives, as well as in
metallurgical operations; and in order to supply the demand, large
quantities of coal are "coked," a process by which the volatile products
are completely combusted, pure coke remaining behind. This process is
therefore the direct opposite to that of "distillation," by which the
volatile products are carefully collected and re-distilled.

The sulphurous impurities which are always present in the coal, and which
are, to a certain extent, retained in coke made at the gas-works,
themselves have a value, which in these utilitarian days is not long
likely to escape the attention of capitalists. In coal, bands of bright
shining iron pyrites are constantly seen, even in the homely scuttle, and
when coal is washed, as it is in some places, the removal of the pyrites
increases the value of the coal, whilst it has a value of its own.

The conversion of the sulphur which escapes from our chimneys into
sulphuretted hydrogen, and then into sulphuric acid, or oil of vitriol,
has already been referred to, and we can only hope that in these days
when every available source of wealth is being looked up, and when there
threatens to remain nothing which shall in the future be known as
"waste," that the atmosphere will be spared being longer the receptacle
for the unowned and execrated brimstone of millions of fires and
furnaces.




CHAPTER VII.

THE COAL SUPPLIES OF THE WORLD.


As compared with some of the American coal-fields, those of Britain are
but small, both in extent and thickness. They can be regarded as falling
naturally into three principal areas.

The northern coal-field, including those of Fife, Stirling, and Ayr
in Scotland; Cumberland, Newcastle, and Durham in England; Tyrone
in Ireland.

The middle coal-field, all geologically in union, including those of
Yorkshire, Derbyshire, Shropshire, Staffordshire, Flint, and
Denbigh.

The southern coal-field, including South Wales, Forest of Dean,
Bristol, Dover, with an offshoot at Leinster, &c., and Millstreet,
Cork.

Thus it will be seen that while England and Scotland are, in comparison
with their extent of surface, bountifully supplied with coal-areas, in
the sister island of Ireland coal-producing areas are almost absent. The
isolated beds in Cork and Tipperary, in Tyrone and Antrim, are but the
remnants left of what were formerly beds of coal extending the whole
breadth and length of Ireland. Such beds as there remain undoubtedly
belong to the base of the coal-measures, and observations all go to show
that the surface suffered such extreme denudation subsequent to the
growth of the coal-forests, that the wealth which once lay there, has
been swept away from the surface which formerly boasted of it.

On the continent of Europe the coal-fields, though not occupying so large
a proportion of the surface of the country as in England, are very far
from being slight or to be disregarded. The extent of forest-lands still
remaining in Germany and Austria are sufficing for the immediate needs of
the districts where some of the best seams occur. It is only where there
is a dearth of handy fuel, ready to be had, perhaps, by the simple
felling of a few trees, that man commences to dig into the earth for his
fuel. But although on the continent not yet occupying so prominent a
position in public estimation as do coal-fields in Great Britain, those
of the former have one conspicuous characteristic, viz., the great
thickness of some of the individual seams.

In the coal-field of Midlothian the seams of coal vary from 2 feet to 5
feet in thickness. One of them is known as the "great seam," and in spite
of its name attains a thickness only of from 8 to 10 feet thick. There
are altogether about thirty seams of coal. When, however, we pass to the
continent, we find many instances, such as that of the coal-field of
Central France, in which the seams attain vast thicknesses, many of them
actually reaching 40 and 60 feet, and sometimes even 80 feet. One of the
seams in the district of St. Etienne varies from 30 to 70 feet thick,
whilst the fifteen to eighteen workable seams give a thickness of 112
feet, although the total area of the field is not great. Again, in the
remarkable basin of the Saone-et-Loire, although there are but ten beds
of coal, two of them run from 30 to 60 feet each, whilst at Creusot the
main seam actually runs locally to a thickness varying between 40 and 130
feet.

The Belgian coal-field stretches in the form of a narrow strip from 7 to
9 miles wide by about 100 miles long, and is divided into three principal
basins. In that stretching from Liege to Verviers there are eighty-three
seams of coal, none of which are less than 3 feet thick. In the basin of
the Sambre, stretching from Namur to Charleroi, there are seventy-three
seams which are workable, whilst in that between Mons and Thulin there
are no less than one hundred and fifty-seven seams. The measures here are
so folded in zigzag fashion, that in boring in the neighbourhood of Mons
to a depth of 350 yards vertical, a single seam was passed through no
less than six times.

Germany, on the west side of the Rhine, is exceptionally fortunate in the
possession of the famous Pfalz-Saarbruecken coal-field, measuring about 60
miles long by 20 miles wide, and covering about 175 square miles. Much of
the coal which lies deep in these coal-measures will always remain
unattainable, owing to the enormous thickness of the strata, but a
careful computation made of the coal which can be worked, gives an
estimate of no less than 2750 millions of tons. There is a grand total of
two hundred and forty-four seams, although about half of them are
unworkable.

Beside other smaller coal-producing areas in Germany, the coal-fields of
Silesia in the southeastern corner of Prussia are a possession unrivalled
both on account of their extent and thickness. It is stated that there
exist 333 feet of coal, all the seams of which exceed 2-1/2 feet, and
that in the aggregate there is here, within a workable depth, the
scarcely conceivable quantity of 50,000 million tons of coal.

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