May 12, 1916.

THE COLLIERY GUARDIAN.

909

Micro=Chemical Examination of Coal in Relation to its Utilisation.*

By J.

The present paper is different from those on the
microscopical examination of coal published during the
last four years in the Transactions of the institute, in so
far as it is intended to give, alongside the microscopical
’ examination, a more or less chemical examination of the
same parts of the seam, so that one can*corroborate the
results of the one by the other. It will be found that
the two together are exceedingly useful in determining
the various qualities of coal and their uses.

The author has been engaged for many months on a
systematic micro-chemical examination of coal, in some
cases embracing the whole thickness of a seam. The
chief object was to see if the various beds showing
different microscopic structure were alike or not, in
giving off the various products on carbonisation and dis-
tillation; and, if not, why? For instance, why does
one part of a seam give off less gas, and make inferior
coke, than another? Why do some seams -coke and
others not? What are the substances, and how to dis-
tinguish them, that are good or bad for producing gas,
coking, or giving off light and heavy tars, for carbonising
at low or high temperatures, or suitable for tarless and
coalite fuels?

Some time ago the author made for Sir W. Garforth
a series of sections of the whole thickness of the Roger
seam; and these preparations, along with the samples
from which they were cut, may serve for the purpose of
demonstration. The seam itself is a good one for the
purpose, having in its composition the various consti-
tuents which are essential in giving extra good or bad
results in its utilisation, although the whole seam taken
altogether is excellent.

It is desirable that some idea should be given as to
the methods used in the process of carbonisation, etc.,
also to the preparation of the sections and. their con-
nection with the pieces carbonised.

Preparing the Sections.

A complete sample of the seam from the floor to the
roof was got, large enough for solid pieces to be cut from
it, these being of various lengths, from 1 or 2 in. to
6 or 7 in., according to the distance between the part-
ings, the cut pieces could then be placed together,
forming a more or less complete square column of coal,
from floor to roof. Each of the pieces was numbered
and lettered, and sections were cut from them accord-
ing to the vertical height of each piece. At the finish
a more or less complete transparent section of the seam
was joined together in a suitable frame, showing the
organic bodies and constituents in the vertical plane.
Also a number of horizontal sections were cut at right
angles to the vertical, or parallel to the bedding plane,
at regular intervals of about 1 in. Such sections show
the various organisms in their lateral plane.

From each of the remaining blocks from which the
vertical sections were made, pieces corresponding to the
sections were cut, and thin slices weighing 100 grammes
were retorted in experimental retorts, one series at a
temperature, of 800 degs. to l,000 degs. Fain*., and
another series at a temperature of 1,800 dogs, to 2,000
degs. Fahr., the first being about the heat at w'hich a
low temperature carbonisation would be carried for
making coalite or smokeless fuel, and the second about
the same heat used in modern gas making, coking, and
by-product producing plant.

' The retorts were arranged so that the volatile matter,
such as gas, ammoniacal liquor, tar, etc., could bo
collected, weighed or measured, and used for fractional
distillation. By these means it could be estimated what
part, or portion, of a seam gave off any particular sub-
stance in-a liquid, or gaseous state, the amount, quality,
and illumination power of gas, the coking and non-
coking qualities and the amount of ammonia, the rest
consisting mostly of the liquid hydrocarbon bodies, etc.

The micro-sections thus show the position, form and
colour of tlie various constituents in the coal. ’Whether
they are composed, of the fructiferous organs, leaf
tissues, twigs, or stems of plants belonging to the
lycopods, cquisetaccce, or gymnosperms. Also the
resinous and other'bodies which may be found in a seam
of coal.

The carbonisation of the corresponding parts shown
in the sections gives the value or behaviour of each
different stratum or substance, whether it is good or bad
for volatilisation and by-products, gas or coking purposes,
in either low or high temperatures. And it will be
seen, on examination of the sections and the chemical
results of the corresponding portions, what parts of a
seam are useful for some purposes and not for others,
the reason why some coals will coke and others not,
and above all, how, by judicious mixing and separating,
a non-coking can be made into a coking coal, at high
or low temperatures.

Roger Seam Coal.

This seam consists of one bed about 5 ft. 6 in. thick,
having at the top a thin bed of siliceous rock. In the
seam are several partings at varying intervals, caused
mostly by thin lamime or layers of charcoal (mother of
coal).' They are not always regular, but sometimes vary
from 6 to 12 in. in the vertical height of the seam.. The
bottom portion of the seam consists of a bright, lustrous
and softish coal, breaking up into more or less cubical
pieces, this being gradually replaced by a hard, dull,
bony-looking coal to a height of 3 ft. 6in. to 4 ft., when
it in turn is replaced by a soft coal similar in appear-
ance to the bottom portion of the seam. This
arrangement of soft and hard coal is common to a large
number of seams, a phenomenon which the writer
endeavoured to explain in a recent paper on “ The
Formation of Coal Seams.”

* From a paper read before the Manchester Geological
and Mining Society.

LOMAX.

On examination of the sections from the base of the
seam we find that the coal is composed of a fairly
divided humus, mainly derived from small fragmentary
plant tissues, with here and there groups of sporangia,
containing spores, many belonging to the equisetaccce
and pteridospermece. One vertical section shows a
large number of resinous bodies, some oval in form,
other ribbon-like, whilst another shows a number of
laminae composed of leaf and other fine tissues, and the
corresponding horizontal section a portion of a long
section of the woody cylinder of a catamite stem, the
lighter strands being the inner edges of the radiating
woody wedges of the stem.

The above represent a thickness of 7 or 8 in. of bright
soft coal, without any definite or striking bands or lami-
nations, being fairly homogeneous.

As already mentioned, as we ascend upwards in the
seam, a gradual change takes place in the coal sub-
stance, the constituents becoming more varified and
distinct. A higher vertical section is found to be made up
of thin alternating bright and dull-looking laminae, the
dull parts being composed mainly of a species of mega-
spores, with thin walls covered with small tubercles. The
megaspores are of a relatively large diameter, and are
very conspicuous in a good horizontal section. The
ground mass where the laminae arc thickest contains
large numbers of fine microspores, in the natural posi-
tion they would occupy when enclosed in their parent
sporangia. The lighter or brighter laminae are chiefly
composed of the more highly resinous bodies, leaf, and
jetonised wood tissues. A number of the small mega-
spores have comparatively thick walls, the large flattened
mass on the top side being a portion of a flattened fruit
cone.

Another vertical section, taken through a portion of
a steam of cordiatcs, shows the wood tissues cut longi-
tudinally, the characteristics pitted vessels similar to
the recent pines being exceedingly well preserved.
Another vertical section shows a similar stem cut trans-
versely, the ends of the vessel being well shown,
although the stem is crushed and contorted somewhat.
This portion is composed of a large number of small
resinous and spore-like bodies. Other sections in this
region show the matrix, or ground mass, to be composed
of more or less fragmentary plant remains, such as
leaflets and pinnules. One species of megaspores have
thin Avails covered with short appendages having a
bulbous or clubbed end.

To the height of I ft. 8 in. from the floor the coal is
bright, and in places soft. In the upper part there
appear several more or less dull bands of megaspores,
increasing in number upwards, until at about 1ft. Ilin,
the coal is becoming hard and bony-looking, turning
almost completely into a spore coal. The dull-looking
bands are composed of megaspores in a matrix of
microspores, whilst the blight bands show the mega-
spores to be in a matrix or ground mass of fine humic
matter.

Upwards from here to about the height of 3 ft. 4 in.
it is a spore coal, i.c., composed -mainly of large and
small spores, megaspores, and microspores. The mega-
spores in the lower portion are comparatively large in
diameter, having their outer walls ornamented with
protuberances and appendages, some club-like, others
tuberculated, some smooth, and others ribbon-like.

In the same region there are many places where
lamime can be found which arc composed of leaf cuticles
or tissues. "Wood tissues are prevalent in many places,
many of them being extremely bright jet-like lenticular
patches (portions of stems or branches). The micro-
spores in many places are very large and well preserved.

In many places in the sections other bodies can be
found which have not been photographed, some being
the remains of insects. Towards the upper part of the
spore coal the megaspores become less and attenuated,
similar spores being found all the way upwards to a
height of 3 ft. 8 in., and forming the bulk of the coal in
this region. At a height of 3 ft. 4 in. there is a band
containing a. large number of globulites and pyritica
stellate.

From 3 ft. 8 in. tno coal rapidly becomes soft and
bright looking, the laminations thin, the texture fine.
There are many bands above 3 ft. 8 in. which contain
mdcrospores and megaspores, but they are not so thick
or numerous to make it a spore coal. The coal sub-
stance in the upper region is chiefly composed of finely
laminated layers of leaf-like tissues interspread with a
large amount of resinous matter, these conditions
obtaining to the full height of the seam.

This condition makes the coal highly volatile, and
similar to the bottom portion, and moreover demon-
strates that the vegetable debris forming many of our
coal seams was laid down in a natural sequence, mainly
from the droppings of leaves, fruits, twigs, branches,
and sometimes stems of plants of that period. First
as shown by the sections, there would be a growth of
plant life of a low order, which in time formed a humus,
in which plant life of a relatively higher order could
flourish; and this sequence would repeat itself, till
ultimately one class of plants became predominant,
crowding out nearly all others, until they in turn
became so weak, through having to exist in their own
humus (or possibly by some local climatic conditions
caused . by the vast forests they inhabited) that they
allowed other classes and species of plants to establish
a footing in their place, thus effecting the alterations
shown by the sections. First a soft humic coal with a
fair amount of resinous matter in its composition, after-
wards changing gradually into a semi-spore coal, from
which was evolved a complete spore coal, this in turn
again becoming a semi-spore coal and ultimately a
humic coal of a resinous nature.

It may be asked why the above affects the utilisation
of coal in its uses? The reply is that, by analogy, we
find that recent plants give off different products accord-
ing to their nature and species. This is shown, for
instance, by the resin content of the following :—

Per cent.

Yew.........	7'5

Fir ........ 2-7

Larch ...... 1*8

Pine........	1’7

Per cent.

Maple ....... 1*6

Ash ......... 1*4

Beech ....... 1*4

Birch ....... 1*6

Also when we take into consideration the chemical
composition and quantities of carbon oxygen, hydrogen,
and nitrogen, from wood to coal, we see that the altera-
tion occurs in the quantities of these elements, mainly
in the proportion of oxygen, becoming less from wood to
anthracite. This being so, we should expect that, coal
being of vegetable origin, there would be a difference in
seams that had one portion formed of vegetable humus
of one kind, and another of another, according to the
vegetation at that time dominant.

(To be continued.)

KEROGEN AND KEROGEN SHALES.

In the course of a paper read before the Institution of
Petroleum Technologists, Mr. E. H. Cunningham Craig
referred to kerogen as being 'a very useful term, first
employed by Prof. Crum Brown, to denote the substance
or substances contained in Scottish oil shales from which
the oil was obtained. It was roughly defined as being
neither petroleum, bitumen, nor resin, but yielding
petroleum and ammonium compounds on distillation.
A “ kerogen shale ” was a shale containing kerogen, and
was distinguished from a shale containing crude
petroleum or bitumen, which was entitled equally with a
kerogen shale to be called an oil shale. With regard to
the origin of kerogen, and the manner in which it bad
become associated with argillaceous beds to form kerogen
shale, it was evident that kerogen was to be found in
other deposits besides kerogen shales. Almost every
coal, especially cannel coal and coking coal, yielded
petroleum on distillation, and did not yield it by treat-
ment with solvents, and, therefore, might be said to
contain kerogen.

Dealing with the results of microscopic research into
the incidence of petroleum, the author led up to the fact
that the association of petroleum with yellow bodies of
irregular size and shape seemed to be thoroughly estab-
lished. All oil shales were stated to contain them, and
the yield of oil was said to be in direct proportion to the
number of yellow bodies, though the oils distilled
differed in some ways from crude petroleum, principally
by containing very small percentages of petrol or
naphtha. The question of these yellow bodies had been
gone into very thoroughly; a number of microscopic
slides had been cut specially from specimens of Scottish
torbanite, and several of the best-known Scottish oil
shales; and the author had examined a large number of
slides of Autun and Kentucky boghead coals, Australian
and Scottish torbanite, and oil shales from Scotland,
South Africa and Bulgaria. The result of such examina-
tion led to the conclusion :—(1) That the yellow bodies
are not vegetable fossils of any kind, neither algae nor
spores; (2) that the kerogen has .been developed in, or
has been introduced into, the deposits since they were
formed; (3) that in the case of torbanites or boghead
coals, the kerogen seems to have developed in situ, to a
great extent at least; (4) that in the case of ordinary
oil shales, the kerogen may largely have been introduced
from some outside source.

The chemical evidence obtainable from analyses of
various specimens of kerogen served to suggest a rela-
tionship such as that indicated by Prof. Jeffreys in his
conclusion that the yellow bodies in torbanites and bog-
head coals were the mother of petroleum; a family
resemblance between the descendants of petroleum-
manjaks, asphalt, etc.—must be admitted.

The author also pointed out that by a study of the
conditions and environment in which oil shales existed
in different countries much could be learned. It was
frequently noticed that the shales richest in oil wore
often the poorest in ammonium sulphate, and also that
the older shales were, compared vviith the younger, richer
in ammonium sulphate and poorer in yield of oil. Per-
haps, however, the most interesting and significant
phenomenon in connection with the Scottish oil shales
was that a shale when traced far, especially beyond (.he
confines of an anticlinal area, passed into ordinary
carbonaceous shale; it still retained the carbonised
remains of vegetable matter which was frequently
detected in oil shales, but it lost the kerogen. Some-
what similarly a bed of shale might pass almost
insensibly upwards or downwards into barren “ blaes.”

Oil shales were always associated with argillaceous
deposits, and were , almost invariably overlain, by
impervious shaly strata or close grained ironstone bands,
but porous sandstones were frequently found beneath
them, sometimes in actual contact, but more often at a
short distance. Many of these sandstone beds were of
great thickness, and were freestones, i.c., free from
close grained cementing material, such as carbonate of
lime. They contained the .casts of vegetable fossils,
such as tree trunks, but little or no carbonaceous matter.

There was a very close association between torbanite
and coal, indicating that it was a different type of deposit
from the true oil shales, though resembling them by con-
taining kerogen. The yield of oil from torbanite ran as
high as 130 gals, per ton, but the yield of ammonium
sulphate was low, being about 101b. per ton.

The evidence from oil fields proved that substances
indistinguishable from kerogen were formed by the
inspissation of petroleum, and by the adsorption of
inspissated petroleum by argillaceous material.

Finally, the author claimed that a review of the
evidence — microscopic, chemical and. geological —
showed that there was a fairly complete case for attri-