June 14, 1918.

THE COLLIERY GUARDIAN.

' 1195

MANCHESTER GEOLOGICAL AND
MINING SOCIETY.

THE MICRO-CHEMICAL EXAMINATION OF COAL.

A meeting of the members was held on Saturday,
June 8, at the works of the Lomax Palaeo Botanical
Company, Okenbottom, Tonge, in order that they
might acquaint themselves personally with the re-
searches into the chemical and botanical structure
of coal carried on by Mr. J. Lomax.

The Secretary (Mr. N. Williams) read a paper
written by Mr. Lomax on “ The Micro-Chemical
Examination of Coal in Relation to its Utili-
sation.” The statements and conclusions set
forth of the three papers already presented
to the society by the author were based mainly
on what had been revealed by the microscopical
examination of thin slices or sections, and in the
present paper he intended to combine microscopical
examination with a chemical examination of the same
parts of a seam, so that the results of both could
be correlated. The two together were exceedingly
useful in determining the qualities of coals and the
uses to which they could be put. For this purpose
the microscope was quite as important as the retort,
and must not be regarded merely as a toy or a scien-
tific curiosity.

During the last few years many papers had been
read on the utilisation and conservation of the coal
supplies in this country. Everyone admitted the
paucity of our knowledge as to the nature of the con-
stituents found in a given seam of coal, and how
that coal could be applied to the best advantage. He
had been engaged for many months on a systematic
micro-chemical examination embracing the whole
thickness of a seam, to find out whether beds different
in their microscopical structure were similar in the
products given off on carbonisation and distillation,
and, if not, what was the reason. Why did one part
of a seam give off less gas and yield inferior coke,
as compared with another? Why did some seams
coke, and others would not? What substances were
good or bad for producing gas, for coking, for giving
off light or heavy tars, for carbonising at low or
high temperatures, for producing tarless or coalite
fuels? How could these substances be distinguished?
The results of the investigation were excellent, and
in many cases far beyond expectation.

Methods of Preparation.

In the first place it was desirable to give some idea
as to the methods employed. A complete sample was
taken of the seam, from the floor to the roof, of such
a size that solid pieces could be cut from it varying
in length from 1 or 2 in. to 6 or 7 in., according to the
distances between the partings. The cut pieces could
then be placed together, forming a more or less com-
plete square rod of coal. Each piece was numbered
and lettered. Sections were cut from them according
to the vertical height of each piece, and at the finish
a more or less complete tranparent section of the seam
was formed together in a suitable frame, thus show-
ing the organic bodies and constituents in the vertical
plane. Also at regular intervals, with about 1 in.
space between, horizontal sections were cut at right
angles to the vertical or parallel to the bedding plane.
These showed the organisms in the horizontal plane.

For the purposes of the chemical investigation,
pieces corresponding to the sections were cut into thin
slices weighing 100 grammes, and were heated in
experimental retorts. One series was brought to a
temperature of 450 to 500 degs. Cent., that being
about the heat at which low temperature carbonisa-
tion was employed for making coalite or smokeless
fuel. Another series was brought to about the same
heat as was used in modern gas making, coking and
by-product plants, viz., 1,000 to 1,200 degs. Cent.
At an intermediate or medium temperature—viz., 650
to 700 degs. Cent.—the carbonisation was carried out
mainly for the purpose of finding what was the ulti-
mate effect of heat on the various resinous, humic,
spore and other laminated bands in the coal. Instead
of breaking the coal into small pieces, it was cut of
a sufficient size to be put in the retort whole. The
retorts were arranged so that volatile matter (such
as gas, ammoniacal liquor, tar, etc.) could be collected
and weighed or measured and used for fractional dis-
tillation. By these means one could ascertain what
portion of a seam gave off any particular substance
in a liquid or gaseous form, and the quantities, quali-
ties, and properties of the products.

The micro section showed the position, form and
colour of the constituents in the coal, and whether
they were composed of the fructiferous organs, .
leaf tissues, twigs, or stems of plants. It also indi-
cated what resinous and other bodies were present.
The carbonisation of the corresponding portions indi-
cated whether they were good or bad for volatilisa-
tion, for gas or coking purposes, or for procuring
by-products, by either low or high temperature pro-
cesses. In this way, by means of the microscope and
retort, it was possible to ascertain what parts of a
seam were useful for particular purposes, and by
judicious mixing and separating, a non-coking coal
could be made into a coal coking either at high or
low temperatures.

The Roger Seam, Dukinfield.

Some time ago Sir W. Garforth commissioned the
author to make a series of micro sections of the
whole thickness of the Roger Seam, Dukinfield. These
were exhibited in the society’s rooms and afterwards
presented to the Victoria University, together with
coked samples and ashes, and he now proposed to use
them for the purposes of his demonstrations.

The seam itself was a good one for the purpose. It
consisted of one bed about 5 ft. thick, having at the
top a thin band of siliceous rock, and there were
several partings of thin laminae or layers of charcoal.
These partings were not always regular; they varied
from 6 in. to 12 in. in the vertical height of the
seam. The bottom portion up to a height of 1 ft. 3 in.
from the floor consisted of a bright, lustrous coal,

soft in places, which broke up into more or less cubical
pieces. It gradually changed into a hard, dull, bony-
looking coal (at 1 ft. 11 in.), which was followed by
a soft coal similar in appearance to the bottom por-
tion of the seam. In the sections taken from the
base of the seam, the coal was seen to be composed
of a finely-divided humus, mainly derived from small
fragmentary plant tissues. Occasionally there were
groups of sporangia containing many spores of the
ferns Equisetinae and Pteridospermae. In one of the
vertical photo-micrographs there were a large number
of resinous bodies, some oval in form, others frag-
mentary. Similar bodies with fragmentary pieces of
wood tissue were to be seen in their horizontal plane
in the corresponding horizontal photo-micrograph.
Another vertical photo-micrograph showed a number
of laminae composed of leaf of fine humus, and the
corresponding horizontal photo-micrograph showed a
portion of a long section of the woody cylinder of a
calamite stem, the lighter strands being the inner
edges of the radiating woody wedges of the stem.

The sections described represented a thickness of
7 in. or 8 in. of bright soft coal devoid of any definite
or striking laminations or bands. A gradual change
took place vertically in the coal substance, the con-
stituents becoming more varied and distinct. The
first vertical section referred to above was made up
of thin laminae, the dull parts being composed mainly
of a species of megaspores with thin walls covered
with small tubercles. The megaspores were of rela-
tively large diameter, and very conspicuous in a
good horizontal section. The ground mass where the
laminae were thickest contained large numbers of fine
microspores. Still another photo-micrograph repre-
sented a portion of coal with the microspores in the
position they would occupy when enclosed in their
parent sporangia. The light or brighter laminae
were chiefly composed of more highly resinous bodies,
leaf and jetonised wood tissues.

. Mr Lomax then described in detail the charac-
teristics of a number of photo-micrographs. One, he
said, was taken through a portion of a stem of cor-
daites, showing the wood tissues cut longitudinally;
the characteristic pitted vessels, similar to pines, were
well preserved. A similar stem cut transversely was
shown in another; the stem was crushed and some-
what contorted, but the ends of the vessels were well
shown. In other cases one observed a large number
of resinous and small spore-like bodies; a large mega-
spore having its outer walls covered with large fila-
mentous appendages; a ground mass composed of more
or less fragmentary plant remains; the fragmentary
leaves and pinnacles; cuticles of cordaites leaves; a
species of megaspore which had thin walls covered
with short appendages having a bulbous or clubbed
end.

These samples were taken from the bottom portion
of the seam. As the distance from the floor increased
there appeared several dull bands of megaspores which
became more and more numerous until at about
1 ft. 11 in. the coal was hard and bony-looking. Here
it was composed of megaspores in a matrix of micro-
spores. Thence to a height of 3 ft. 4 in. it was a spore
coal composed mainly of megaspores and microspores.
In the lower portion the megaspores were compara-
tively large in diameter, having on their outer walls
protuberances and appendages, some club-like, others
tuberculated, some smooth, others ribbon-like. In
the same region were found laminae composed of leaf
cuticles or tissues. Wood tissues were prevalent in
many places; they were often present as extremely
bright jet-like lenticular patches representing portions
of stems or branches. In many places other bodies
could be found which had not been photographed;
some of them were the remains of insects.

Towards the upper part of the spore coal the mega-
spores became fewer and attenuated. Then at 3 ft.
4 in. there was a band containing a large number of
globulites and Pyritica stellata. From 3 ft. 8 in. the
coal rapidly became soft and bright-looking, the
laminations thin, the texture fine. Of course there
were many bands which contained spores, but they
were not present in such quantities as to make it
a spore coal. Some of the megaspores were very
interesting, being of the same species as some recently
figured and described by Mrs. R. Scott, F.L.S., as
Lepidostrobus Fobaceous, from the lower coal
measures. Taken as a whole, in the upper region
the coal substance was chiefly composed of finely
laminated layers of leaf-like tissues interspersed with,
a large amount of resinous matter. This structure
made the coal highly volatile and similar to the bottom
portion.

It was clear that the vegetable debris derived from
the dropping of leaves, fruits, twigs, branches, and
sometimes stems of plants, was laid down in a natural
sequence. In the first place there would be a growth
of plant life of a low order, producing in time a
humus in which plant life of a relatively higher order
could flourish. This sequence repeated itself until
ultimately one class of plants became dominant and
crowded out all the others. In turn, whether because
that class became weak through having to exist in
its own humus, or possibly because of some modifica-
tion of the local climatic conditions, other classes and
species of plants were allowed to establish themselves.
This would cause the changes seen in the sections.
First a soft, humic coal with a fair amount of resinous
matter in its composition, changing gradually into
a semi-spore coal, then developing into a com-
plete spore coal, which was succeeded by a semi-spore
coal, and ultimately a humic coal of a resinous nature.

It might be asked how this affected the utilisation
of coal? The reply was that different plants yielded
different products according to their nature and
species. Take, for instance, the resin contents. The
yew contained 7-5 per cent, of resin, fir 2-7, larch 1-8,
pine 1-7, maple 1*6, ash 1*4, beech 1'4, birch 1'6.
Moreover, alterations occurred in the quantities of
the elements, carbon, hydrogen, nitrogen, and oxygen
present. One would therefore expect that the coal,
being of vegetable origin, would vary in the same
seam, one portion differing from another in its charac-
teristics according to the vegetation which happened

to be dominant at the time it was formed. This
theory was confirmed by the results obtained from
various samples of carbonised coal from the Roger
seam.

Carbonisation.

This part of the paper dealt with the methods and
results of the carbonisation of pieces of coal corre-
sponding to the sections previously described.
Samples of equal weight were taken and heated to
uniform temperatures. The carbonisation was carried
out in three temperatures: —

Low, from	450	to	500	degs.	C.,	Series	A.

Medium ,,	650	to	700	degs.	C.,	Series	B.

High ,,	1,000	to	1,200	degs.	C.,	Series	C.

The coked residue from each sample	was preserved

in a rectangular glass box for the purpose of examina-
tion with the corresponding sections.

In Series A the temperature was about the same
as would be used in carbonisation for coalite, smoke-
less, or tar fuels. The coke produced was a dead
black in colour. In Series B the object was to ob-
serve the changes in the various bands and laminae
of the coal substance above the temperature at which
most of the liquid and volatile constituents were
driven off. All the pieces of coal in this series had
been cut into rectangular blocks in order to see the
effect of carbonisation on their liability to break up,
swell, or puff up, and, above all, the appearance of
the resinous afid non-resinous laminae. The last-
named were brilliant black in colour, but puffed up
from the non-resinous, steel grey matrix. Series C
yielded coke of a steel grey colour, some portions very
hard and compact and others less, according to the
substance from which it was derived. The tempera-
ture employed, .1,000 to 1,200 degs. C., was that
used in modern plants for producing gas, coke, and
by-products.

For many reasons it was considered inadvisable to
publish a full table of the weight and volume of the
coke, gas, ammoniacal liquor, tar, etc., from each
sample, although they had been recorded, but the
author gave a statement of the carbonisation results
from four places in the seam, these particulars serving
to indicate clearly the difference between one part
and another.

Sample No. 1A was a fairly strong and compact
coke, dull black in colour, and hard to break. It was
produced from soft bright coal, taken near the floor
of the seam, which was crushed fairly fine, no pieces
being larger than J in. diameter, and carbonised
for 2-J hours before all the gas was driven off. 1 B was
from the same horizon as 1 A. It was put into the
retort in one piece, but owing to its softness it broke
up. It was subjected to a temperature of 650 to 700
degs. C., and in hours all the gas had been ex-
pelled. The coke had a greasy-looking, swollen and
irregular outline, which indicated that the coal was
of a resinous nature. Sample 1C, taken from the
same place, was crushed to pass through a | in. mesh,
and was retorted-at a temperature of 1,000 to 1,200
degs. C. The result was a bright, metallic-looking
coke, compact in texture. The surface was puffed
in a manner similar to 1B. In carbonisation the
gas and volatile matter escaped through the puffs,
the other side being solid. The yield of gas at the
above temperature was very much in excess of that
obtained at the low temperature, and it was given
off much quicker, but during the latter part of the
process the gas was of a very poor illuminating power.

Examination of the samples of B coked coal, begin-
ning with Series A, showed that the first two samples
were hard and compact. After No. 2 the coke became
more mealy or sandy looking outwardly. This indi-
cated that the coal substance did not coalesce by
heat. . Proceeding upwards it became less coherent,
until in sample No. 7 it was almost non-coherent,
and the coke was almost like meal or sand. From
No. 8 upwards the coke became more solid, the coal
substance coalescing, and at No. 11 the coke was quite
hard and compact, as in samples 1 and 2. The
reason for this became apparent on examination of
the sections and comparison with the corresponding
coke pieces in the Series B. In the former there
was a gradual decrease of the bright, reddish-yellow
resinous bodies and leaf laminae, and a corresponding
increase of the spore contents, especially the mega-
spores, until about the middle part of the seam it
was composed almost entirely of megaspores and
microspores.

Now taking the coked pieces (Series B), the speci-
men 3 B exhibited bands and laminae which were
highly volatile, and thick bands which were flat and
slaty-looking, indicating that these parts were com-
posed of non-resinous substances, chiefly spores. The
other samples were summarised as follows. 4 B:
Bottom part similar to 3B, upper part a thick band
of a slaty character, also a thin band resembling
the bottom part. 5 B : Great increase in the non-
resinous laminae; the ridges caused by the swelling
of the resinous substances were small in comparison
with those in 2B. 6B and 7 B : Coal broken up into
non-coherent slaty-looking pieces. 8 B : Return of
the puffed or swollen laminae of resinous matter, the
slaty parts being dominant. 9 B : Resinous laminae
becoming more dominant; occasional laminae composed
of leaf tissue. 10 B : Patches similar to 9B. 11 B :
A puffed or swollen coke derived from coal substances
of a highly volatile and resinous nature.

The coked samples in the high temperature Series C
furnished corresponding results, with the difference
that the coke was much harder and more metallic-
looking. 3 C, 4 C, and 5 C showed a fairly good coke.
6 C and 7 C poor quality similar to breeze from gas
works. 8 C and 9 C much better. On the outer sur-
faces the small pieces were luted together by
resinous matter. 10 C and 11C, strong, excellent
metallurgical coke. By mixing the bottom or top
softs with the non-coking spore coal a good coke could
be obtained, and the gas and the tar products were
improved, especially when compared with the spore
coal itself.

The ashes were also interesting, because the colour
indicated where they were derived from. Ash from