> September 29, 1916.

THE COLLIERY GUARDIAN.

60S

BRITISH ASSOCIATION FOR THE
ADVANCEMENT OF SCIENCE.

(Continued from page 555.)

CHEMICAL AND GEOLOGICAL CHARACTERS
OF COAL.

On Thursday, September 7, a joint meeting of
Sections C (Geology) and B (Chemistry) was hold on
“ The investigation of the chemical and geological
characters of different varieties of coal, with a view to
their most effective utilisation as fuel and to the extrac-
tion of by-products.”

Prof. G. A. Lebour, in opening the discussion, said
the attitude or relation of geologists and chemists to
the matter of coal was rather a peculiar one. The
geologist had to find the coal before it could be treated
by the chemist; but geologists could very seldom tell
what kind of coal it was they found, and therefore they
had to turn to the chemists for advice in the matter.
Some authoritative classification of coal should be
arrived at, which should be to the satisfaction of both
chemists and geologists, and be a fairly easy one. One
thing he would like the chemists to do was to give some
kind of uniformity in the analysis of coal, for geologists
frequently were at a loss how to make use of the
analyses, owing to the different ways in which they
were expressed. Sometimes the only evidence of coal
was in the very small pieces brought up by boring; and
very often two coals were identical as far as outward
appearances were concerned; but that was where the
chemists came in and found out the chemical pro-
perties. Sometimes, however, two coals had practically
an identical composition, according to the analysts, but
they differed in physical properties; and since it was
the physical properties that were of interest to industry
and the world in general, they would like, if possible,
to have a definition of coal which might comprise all
sorts of schedules such as coking, physical, and
chemical properties. Geologists regarded coal as a rock
which was usually found in layers with roof and floor.
The floor and roof both varied, and according to the
variety and difference in the roof, there should be a
corresponding difference in the nature of the coal.
Sometimes a difference in the nature of the coal was
found, and sometimes not. They were told that, in
that district, for instance, with a post or sandstone roof
instead of shale, the coal was found to be of a worse
quality than when the roof was of shale. That was
what they expected to find, but sometimes the coal
under a sandstone roof was as good as, and even better,
than the other. Those were points he (the speaker)
would like the chemists to explain. The floor was
generally more uniform than the roof, being generally
of fireclay or ganister rock; yet the siliceous deposits
were free from certain ingredients which were usual
in most clays, but more or less absent in others. When
there was no fireclay of that kind, they should find
some difference in the nature of the coal above it, but
very frequently they did not. Those were questions
they would like chemists to answer, and very often
chemists had to investigate lumps of coal without the
slightest knowledge as to the conditions in which the
coal was secured. If chemists were given these parti-
culars, they could take into consideration the circum-
stances, which would probably enable them to explain
the phenomena that had been a great difficulty and
drawback. He had been connected with coal for about
50 years, and the more he studied it the less he seemed
to know about it.

Methods of Analysis.

Prof. W. A. Bone, F.R.S., thought the feeling of
most chemists on the subject would be that of the
great difficulty of saying anything at all, as there was
not much to say of a definite character. They usually
applied certain tests to coal, to- secure information
regarding specific uses for commercial methods accord-
ing to the experiences of different analysts, and used
tests which had been found to be more or less satis-
factory. They could determine the carbon, hydrogen,
and organic nature with a certain amount of precision,
but too frequently those results came out differently,
according to the amount of air. These tests would not
give much help to the geologist in determining the real
nature of coal. On going further, they found that,
during the past 20 or 30 years, the problem had been
attacked on different lines, some studying the effect of
some chemical agent or solvent upon the coal substance.
More recently they had been studying the action of
pyridine, which removed and dissolved certain consti-
tuents in the coal; and a good deal of work had been
done in other methods of attacking coal, but very little
had been done in the way of correlating or bringing the
different methods to a focus, and to see them in their
proper perspective. Those members, of the chemical
section who were dealing with the chemical constitu-
tion of coal, were endeavouring to embody the results
of the last 20 or 30 years’ investigations of the chemical
construction of coal. It was very difficult when they
saw the different results obtained by different experi-
mental methods. They had decided to begin their
investigation of the subject by repeating -some of the
older work and methods in the same laboratory, and
having the results compared. Until that work was
carried out, he did not think chemists were in a posi-
tion to say very much about the exact chemical nature
of the substances found in coal. They knew something
in a general way of the types of coal, but many of the
methods had not always been performed in a suffi-
ciently experimental manner. He had found in cer-
tain cases that it was necessary to exclude the presence
of oxygen, and a good deal of care would have to be
taken in ascertaining what protection must be applied
and methods adopted for curtailing the amount of air.

In their work they would require the assistance of the
geologists.

Prof. Kendall said he looked at the question from
the point of view of the working geologist, and was of
opinion that much research was needed in co-operation
with the chemists who were investigating coal in regard
to economies; and geologists should co-operate with the
chemists. There should be a general investigation of
the coal and the coal seams, because an economic
analysis was not sufficient. Coal consisted of very
different material in more intimate subdivisions. There
were bright, lustrous layers and dull charcoal layers, the
bright layers consisting of the bark of trees, and the dull
layers being supposed to consist of trees, smaller branches,
leaves, and so on. When these layers were examined
chemically, they showed a considerable difference, and
seeing that the ash present in coal was one of the factors
controlling its economic use, they would like to know
what the ash was, what was its relation to the original
plant substance, and where it resided. On that point
there had been insufficient discrimination shown in the
different methods of determination. Many years ago
Prof. Green caused investigations of the ash of coal to
be made, with a view to determining where it resided.
It was found that whereas the bright layers yielded the
low percentage of 2 per cent, of ash, the dull layers
gave from 6 to 7 per cent. Dr. Pollard obtained
similar results. He crushed his samples of coal into
small pieces, and separated them into specific gravities
of below and above 1-3. From the samples of 1’2 and
1’3 per cent, specific gravity, described as bright coal,
he got 1’66 per cent, of ash, while in the dull material,
with a gravity of 1*3 and 1-4 per cent., the ash amounted
to 5’2 per cent. In other layers it was found there was
fiv? times as much ash in the dull as in the bright sub-
stances. Therefore the greater part of the ash resided
in the dull layers. It was evident that the ash in coal
must be of three geological kinds. There was the
original mineral constitution of the plants, as found by
chemical tests, sand, and a carbonate brassy material.
No effort had been made to separate these residues. As
to the chemical analysis of the ash, and its significance,
he said, silica was found; iron occurred in variable
quantities; lime was present in high proportion, but
potash was in very low proportion indeed. He could
not conceive that a coal yielding 9 per cent, of carbonate
of lime in its ash could owe that substance to the plant
constituents. He was disposed to think that when
carbonate of lime was found in the ash, it was the
result of extraneous matter introduced by water.

Joint Investigation.

Dr. J. T. Dunn, while agreeing that the work chemists
were doing was being carried out on independent lines,
thought it was very desirable they should know what
others were doing. Geologists, chemists, and botanists
should all be aware of what was being done in each
section. Chemists and geologists had said they knew
very little about coal, but the former were beginning to
grope their way into the nature of coal. They knew
that, by solvents, one part would come out and another
remain, and they practically regenerated them; but that
was really all they knew about the actual chemical
nature of coal. Until chemists knew more about that
they could not hope to present any scientific classifica-
tion to the geologists. The present classifications had
been based upon the principles used for finding out the
practical uses of coal for industrial or chemical pur-
poses. A great number of the analyses of coal had not
been made with any scientific object in view, but for
economic purposes through analyses carried out in
different ways. Chemists would never get very far in
solving the question themselves until they knew the con-
ditions of its formation. Geologists could be of assist-
ance to. the chemists by giving out and putting them in
possession of the whole of the facts and then asking the
chemists to investigate. The composition of coal ash
and how far it existed in the substance before it was
coal could only be found by a combination of geologists,
botanists, and chemists examining varieties of coal from
that particular point of view. The composition of coal
ash varied very widely. In one sample of ash he had
found material for an excellent iron ore, it having con-
tained 20 per cent, of pure oxide. The point he desired
to emphasise was that chemists, botanists, and geolo-
gists should combine and put their problems before each
other. It would have to be done by some large organisa-
tion, and he thought the State should take it up as the
United States and the Dominion of Canada had done,
not only from the point of view of its commercial value,
but from a scientific standpoint as well.

Prof. Bone thought there was every prospect within
the next few months that the State would take up and
grant assistance for investigators of coal. It was partly
the result of a movement, begun at the association’s
meeting at Manchester last year and in various scientific
quarters, regarding the value of the properties of coal.
They had an assurance given that the question would
be dealt with in the very near future.

Prof. Bedson said the problem of the nature of coal
and its constituents had had his attention for years,
and he felt that what little he had done had impressed
him with the difficulty involved in the problem of the
solution of the question of the chemical nature of coal.
He had approached the question technically and scien-
tifically, and tried to get some inkling of those materials
which went together to form coal. They were faced
at once with a variety of materials. In coal taken from
a particular seam they would find its constitution vary-
ing in different parts of the seam. The problem of the
chemist was to find some means of differentiating
between the different substances which formed the mix-
ture. Personally, he had had great success in the appli-
cation of pyridine, which would dissolve up to 30 per
cent, of the coal substance. A larger portion of the
coal remained insoluble, but of its composition they
were ignorant. There were other methods of attack.

The composition varied considerably, and they had not
sufficient knowledge at present to give any dogmatic
information that would be of interest to geologists.

Dr. D. T. Jones spoke of the work he had carried out
with Dr. Wheeler, of the Home Office, and pointed
out that that State department had already done a little
to carry out research work concerning coal. He pointed
out that when the distilling of coal was completed by
solvents, a fibre was found mixed with the resin. They
had reason to believe that 80 per cent, was completely
insoluble. The action of the coal seam as a whole while
under pressure did not bring about a separation of
carbon, but the opposite. By distilling coal, petroleum
could- be obtained, but it could not be of vegetable
origin. Paraffin was not present to any great extent,
but it could be very easily disengaged from the hydro-
carbons. They could only find paraffin in places, and
if they could solve the presence of paraffin as distilled
from the substance, they would be able to tackle a very
difficult problem.

Constituents qf Coal.

Dr. Marie C. Stopes, who had been worikng in con-
junction with Dr. R. V. Wheeler, head of the Home
Office station, said that in dealing with the composition
of coal the chemist was faced with the difficulty that
there were contained in it a number of different com-
pounds which must be separated from one another before
their characters could be determined. The only clue to
their composition was the fact—no longer seriously dis-
putable—that they were of vegetable origin. In esti-
mating the nature of coal unaltered by heat or chemical
action, up to date the chemist had done no more than—
by means of solvents—-roughly to separate coal into two
main classes of constituents which had been termed
“ cellulosic ” and “ resinic.” Of those the cellulosic con-
stituents were separable into twx> groups. Palseobotany
had established the fact that some, if not all, ordinary
bituminous coals were formed from a mixture of various
parts of land plants. No living plant was so simply
divisible into two constituents as was coal into cellulosic
and resinic; cellulose formed the major part of the cell
walls of the soft tissues; resin might be present in special
cells or glands, and might possibly be modified from
various cell contents; but the different portions of even
the simplest land plant were composed of a great variety
of distinct chemical compounds, many of which had
been named and classified by plant physiologists.
Though a number of those substances might be but
slight variations of the cellulose complex molecule, yet
in the living plant they had distinctive work to do, and
had recognisably various morphological and physical
properties. It was not unnatural to assume, therefore,
that those various substances might be the sources of
different chemical compounds now in coal. It would
be readily understood that, were different by-products
from coal traceable to specific parts of plants—and
those plant remains were visually recognisable in the
coal itself—a considerable step might be made in the
knowledge of coals and 'their potentialities. The indi-
vidual plant portions might be isolated by suitable
methods and the substances for which they were respon-
sible, when coal was he-ated, determined. It was on
such work that they were at present engaged, using as
the starting point the instance that the phenols obtained
when coal was destructively distilled were derived from
that particular class of compounds grouped as cellulosic.
As plant mechanisms had evolved many destructive
forms of cellulosic compounds, they thought it was
necessary to ascertain whether the various modifications
of cellulose differed materially in the compounds they
yielded, and if so which part of the plant substance
corresponded to any particular coal derivative. An illus-
tration might be useful. Conspicuous in the construc-
tion of many coals were the small yellow bodies known
as spores. Their walls were formed of a derivative of
cellulose. Were they or were they not still in a condi-
tion to react distinctively to treatment by pyridine?
Those who had experience in the examination of coals
would recognise the practical difficulties in the way of
answering so apparently simple a question, for hitherto
spores had not been recognisable in lump coal, but only
in thin sections, whilst, on the other hand, thin sections
were not suitable for extraction by pyridine.
Nevertheless, the difficulties had been overcome,
and in the insoluble residue of coal extracted
by pyridine they had observed unaltered spores
in large numbers. That proved that the particu-
lar modification of cellulose forming their walls
was one of the cellulosic derivatives insoluble in pyri-
dine. Since some coals were largely composed of
spores, that fact was of some value, more particularly
as spores had a most distinctive appearance, and were
generally recognisable in thin sections. The next stage
in the work was the isolation from coal of a sufficient
number of spores to make possible a chemical exami-
nation to ascertain what particular type of chemical
compounds they yielded on destructive distillation.
Spores, though the most conspicuous, were by no means
the principal constituents of most coals : wood, soft
parenchyma, cork, chlorophyll-containing, or green
tissues of leaves, must all have been almost universally
present in proportions varying in the mass of debris
from which any humic coals were formed. Cuticles,
morphologically very distinctive portions of plants, and
at the same time largely formed of a specific chemical
compound, to which the name cutin had been given,
were conspicuous in the coal substance. They had now
isolated sufficient pure cuticles from coal to distil them
separately. It would be their business to track down
the substances in coal one by one, and to isolate them
in such a form as would render their chemical exami-
nation possible. For that purpose the miscroscope was
necessary, and the chemist alone was unable to inter-
pret what was to be seen on its field: the palaeobotanist
alone could not probe into the chemical composition of
even the plant structures he best recognised. The case
was obviously one for co-operation. The practical aim