December 17, 1915.

THE COLLIERY GUARDIAN

1239

larly interesting results. Several clean fragments were
heated in a vacuum to 212 degs. Fahr, for 119 hours,
and the product was tested at intervals. The samples
yielded in the end an average of 10 to 11 volumes of
gas, of which in the larger amount 1-75 volumes, or 16
per cent., was methane. The average composition of
gas was: Methane, 16-6 per cent.; carbon monoxide,
0-1; carbon dioxide, 0*7; oxygen, 9-4; nitrogen, 73-0.
Most of the gas was given off in the first five hours at
86 to 158 degs. Fahr., but the proportion of methane
increased steadily after five hours at temperatures of 158
to 197 degs. Fahr., probably because more of the
included air had been driven off earlier in the test. How-
ever, the proportion of nitrogen increased steadily after
24 hours to the end of the test. The same samples
were then powdered and heated in a vacuum for 26
hours at 212 degs. Fahr., a process that liberated less
than one-fifth as much additional gas as had been
obtained in the first 24 hours in the lump test. This
gas contained 17-9 per cent, methane, nearly the pro-
portion that was contained in the total volume in the
lump test, and nearly three times as much as came off
in the last 27 hours in the lump test, showing that the
liberation of the methane was greatly furthered by pul-
verising the coal. Some heavier hydrocarbons were also
liberated from the powdered coal, showing that they are
held more tightly. It was also found that different
coals showed great diversity as to volume, rate of
liberation, and proportions of gaseous constituents.

Many determinations have been made of gas content
of German coals. A series, by Broockmann, is of
interest, as showing especially low oxygen content. The
tests were made on coal fragments freed, as far as pos-
sible, from air by standing in vacuum for three days.
The gases were obtained by heating the coal samples to
212 degs. Fahr, for several days, great precaution
being taken to avoid the infiltration of air. The approxi-
mate relative volume was 0-1—1-9, the composition
being: Methane, 12—96 per cent.; carbon dioxide,
3—91; oxygen, 0—5; nitrogen, 2—67; carbon monoxide,
0—9 per cent.

Ghysen gave the results of tests of samples of two
Belgian coals from Marcinelle-Nord mine, one series
being taken from a depth of 3,100 ft. in No. 12 shaft,
and another from the same bed at a depth of 2,920 ft. in
No. 11 shaft. There had been several strong outbursts
of gas from the bed, one of which occurred at a depth of
2,920 ft., blowing out 95 tons of coal. The two shafts
are three-fourths of a mile apart, and are separated by a
great fault; the deeper shaft is generally more gaseous
than the other. Samples of about 17| lb. each, in frag-
ments about 0-6 cu. in. in diameter, were collected every
morning, crushed with steel balls for one hour in a
pulveriser hermetically tight, and tested twice, at
intervals of four hours, in the afternoon. A series of 19
samples from No. 12 shaft yielded gas containing 69-1 to
84-65 per cent, methane (mean, 74 per cent.), with less
than 1 per cent, of oxygen and carbon dioxide, the
remainder being nitrogen and air. A series of 12
samples from No. 11 shaft yielded gas containing 43-5
to 87-3 per cent, methane. The volume of gas in each
test was never less than 1-J- that of the coal. The
increase in quantity of gas given off in the four-hour
interval between the two tests was inappreciable. The
most important feature is the variation in the volume of
gas given off under the same conditions by samples taken
at the same hour and from the same place. By crushing
a sample in two stages of half-an-hour each, and draw-
ing off the gas after each stage separately, a greater
total volume of gas was collected than after continuous
crushing for an hour. For different samples the com-
position of the gas -differed greatly, a variation that
Ghysen believes was due to irregularities in escape of
gas through cracks, and also to differences in original
vegetal composition. Gas was also lost in mining, such
loss naturally being uneven. It was found, also, that
from samples taken in the same vicinity, the volume of
gas given off in pulverisation varied from 2| to 5| times
that of the coal. Similar tests were made, also, of
some samples which had been exposed to air for seven
to nine months. In every case they gave off about 1|
volumes of gases, but the composition of these was
peculiar in that gas from samples from shaft 11 con-
tained from 9 to 14-75 per cent, of methane or other
combustible gases; the gas from samples from shaft 12
contained only 1-5 to 2-8 per cent.

Arnould, in his study of gas outbursts, found that
some coal when placed in a receptacle gave off four
times its volume in gas, and believed that the amount
in the solid coal underground must be greater. Marsilly
found that a pressure of 75 lb. to the sq. in. did not
prevent the issue of gas from coal samples; and the
Austrian Commission found that coal from which gas
had been exhausted in a vacuum could not re-absorb as
much as it held originally. Coal from the Albert mine
at Saarbriicken yielded 2 to 2| volumes of gas.

Tests made by Chamberlin of the volume of gas given
off by various American coals showed not only the
variability in volume and in components, but the varia-
tions under different conditions. Under ordinary air
pressure the Monongah (West Virginia) coal yielded
0-86 per cent, of its volume of methane when powdered
to 30-mesh size, and only half as much at 10-mesh size.
When the coal was placed in a vacuum, the yield was
practically the same. Two other samples yielded much
less. A sample of anthracite from No. 1 mine, at
Nanticoke (Pennsylvania), gave off 3-1 volumes of gas
in three weeks; during the fourth week a further volume
of 0-8, which was nearly pure methane, was given off.
The highest proportion of carbon dioxide found was 0-17
per cent, of the total volume of gas liberated.

Rate of Escape of Gas from Coal.

It has been shown that methane and other gases
escape continuously from coal while it lies undisturbed
underground, while it is being mined, and also for a
long time after it has been mined. The rate of escape
in general is variable, but is without known relation to

the mechanical or granular condition of the coal. Coal
that had lost much gas in mining continued to evolve
methane in the laboratory, one sample liberating three-
fourths of its volume in two weeks, and one and three-
fourths volumes in five months.

Various investigations have shown that there is great
variation not only in the total and relative volumes of
methane given off by coal samples, but in the rate of
emanation as well. In general the methane is given off
more slowly than the carbon dioxide, oxygen, or
nitrogen, sd that in the smaller volume of gases
extracted in the later part of the test its percentage
increased with some samples.

Effect of Crushing.

That size of grain is also an important factor, has been
shown particularly by Charriberlin, who found the rate
of emanation was increased by crushing the coal fine, by
the addition of carbon dioxide, and by placing the sample
in a vacuum. In his experiments the coal was broken
and crushed to coarse powder in an airtight receptacle
connected with a vacuum pump. It is believed that
little gas is lost in taking the coal sample from the mine
and making the laboratory transfer. The crushing,
however, opens a large proportion of pores and minute
crevices, and thus greatly increases the surface from
which the gas is given off. Tests were made with
samples under atmospheric pressure as well as in a
vacuum. Some samples were pulverised for several
hours to ascertain the time factor. A sample from the
Monongah mine, West Virginia, was divided into two
parts; one part was crushed to 10-mesh and the other to
30-mesh size, each part being tested separately. The
results were as follow :—

Relative Volumes of Methane from 10 mesh and
30 mesh Samples of Coal.

Relative volume of

No.	methane to coal,

of	Conditions of test. (----------*------->

test.	30-mesh 10-mesh

sample, sample.

1 ... In vacuum nearly an hour.... 0’88 ... 0 33

2	...	In	vacuum short time, then in CO2	0’89	...	0’38

at atmospheric pressure

3	...	In	air under atmospheric pressure	0’86	...	0’41

4	...	In	pure CO2 under atmospheric	0’91	...	0’44

pressure

5	... In vacuum 3| hours, then in CO2 1'38 ... 0’57

under atmospheric pressure

6	... In vacuum 4 hours, then in hydro- 1’39 ... 0’53

gen and CO2 under atmospheric

pressure

The last two experiments show that the gas does not
escape rapidly, and that time is an important factor. If
the crushing is not delayed, the methane emanation is
practically the same, whether coal is crushed in vacuum
or under normal atmospheric pressure. The gas con-
tinues to escape as time passes. The amount imme-
diately liberated also is independent of outside pressure.

Tests were made both in a vacuum and under full
atmospheric pressure, and several trials were made to
ascertain the time factor up to four hours, with the
following results :—

Volumes and Analyses of Gas from Coal Crushed
in Vacuum.

Constituent.

Methane.	Air. '

dioxide.	(excess).

Per cent. Per cent. Per cent. Per cent.

No. of
sample.

Relative
volume
of gas
to coal.

1	.. o-io ..	.. 39’65 ..	. 2’90 ..	. 48’18 ..	9’27
2 ..	.. 0’12 ..	.. 40-99 ..	. 1’56 .	.. 47’48 ..	. 10’27

Rate of Escape from Lump Coal.

In another test, lumps of coal were placed in a
receptacle from which the air was exhausted in about
20 minutes, the diminution of pressure amounting to
more than 29 in. The air exhausted in 20 minutes from
a vessel containing Monongah coal contained 0-002
volume of methane, whereas coal from the Naomi and
the Mansfield mines gave only a trace of methane. A
fourth sample from a gaseous part of the Monongah
mine gave off 0-003 volume of methane. A sample of
lumps of anthracite coal from No. 1 mine, Nanticoke,
Pennsylvania, gave off 0-03 volume of methane in 20
minutes, and 1-07 volumes in seven days.

Chamberlin made an extended series of tests to ascer-
tain the rate of escape of gas from coal samples during
a period of six months. The coal was stored in vacuum
bottles, and the gas pumped out at intervals for analysis.
The volume of gas and rate of escape depended greatly
on the size of the fragments. At the end of six months
gas was still escaping from lump coal, whereas the
liberation of gas from the crushed coal had nearly ceased.
Samples of one crushed coal yielded 2-3 to 0-9 volumes
of gas, whereas lump samples of the same coal yielded
only 0-5 to 0-9 volume of gas. To investigate the
volume of gas lost in handling the sample, coal was
collected at the face in the mine and placed in cans,
which were at once sealed. The gas in the cans was
determined a week later, and a month later some of
the sample that had been placed in vacuum bottles was
tested. Bituminous coal from the Mansfield mine,
Carnegie, Pennsylvania, gave off 0-55 volume of gas,
exclusive of nitrogen, and gas escaped more rapidly
during the first few days. A sample of gaseous anthra-
cite, however, showed a nearly uniform rate of escape
of methane. Gases other than methane were mainly
air, nitrogen, and carbon dioxide. The rate of escape of
nitrogen decreased with time, showing that the nitrogen
was mainly from residual air that had given up its
oxvgen to the coal.

Deducting extra nitrogen, the proportion of methane
rose as high as 98 per cent, for some samples: but usually
it was between 80 and 95 per cent. The methane per-
centages were highest in the anthracite sample, which
yielded but little carbon dioxide, whereas the bituminous
coal from the Mansfield mine contained as much as 13
per cent, of carbon dioxide.

Lump coal fresh from some mines continues to evolve
gas enough to be lighted in a mine car. Morin cited an

instance in which air extracted from the centre of a
pile of freshly broken coal weighing three or four tons
contained 16 to 26 per cent, of methane.

Rate of Escape from Pulverised Coal.

In order to compare the rate of escape of gas from
finely crushed coal with that from coarse lumps in the
test by Chamberlin, samples from other parts of the
Monongah mine were crushed to pass through a 10-mesh
sieve, and then bottled in vacuum. In general the
proportion of carbon dioxide steadily increased, finally
reaching 15 per cent, in one sample, and nearly 21 per
cent, in the other. The comparison showed that finely
crushed coal gives off much more gas than lump coal;
emanation starts more rapidly, and the proportion of
methane is larger.

Comparative Tests with Different Sizes.

A series of tests was made by Chamberlin to deter-
mine the rate of escape of methane from coals of various
kinds, and especially the relative volumes from the
same coal in small lumps and in powder. The results
showed that methane escapes more freely and in larger
volume from crushed coal, but that the supply more
slowly emitted by the lumps would in time equal that
from the powder. Therefore, the extent to which the
“pores” of the coal are opened affects the rate of
emission, but not the ultimate volume of the gas
liberated, so it is not a matter of volume of gas liberated
in a given time, but of liberation of all the gas in suffi-
cient time. Chamberlin summarised the conclusions
drawn from these results as follow :—

(1)	Reduction of pressure removes gases from coal
slowly—a matter of weeks and months.

(2)	Finely powdered fresh coal gives off more
methane during six months in a vacuum than the
same amount of lump coal subjected to the same con-
ditions. But, presumably during a much longer period
of time, approximately the same volume of gas should
be expected to come off from either type of coal.

(3)	Reduction of pressure for only a few hours, or
even a few days, is far less effective in extracting the
entrapped gas than crushing the coal, either in a
vacuum or under barometric pressure.

(4)	Crushing coal to a certain degree of fineness
yields approximately the same volume of methane,
whether the operation is performed in a vacuum or in
an atmosphere of air or carbon dioxide.

(5)	Crushing the coal to the degree of fineness of
which the crusher is capable removes only a minor
proportion of the free gas stored within the coal, for
Monongah coal already crushed either in vacuum or
under full atmospheric pressure yielded more methane
during two weeks in a vacuum than was liberated
during the crushing.

The conclusions signify that old coal workings and
faces continue to give off gas.

(To be continued.)

BOOK NOTICES.

The South Wales Coal Annual for 1916. Edited by Joseph
Davis and C. P. Hailey.	5 J in. x 8Jin. Cardiff:

Business Statistics Company Limited. Price, 7s. 6d.
net.

In this admirable annual the editors, despite the many
difficulties created by the war, have again arranged a
compendium of information which will prove of great
assistance to those engaged in the staple industry of
South Wales. The present issue continues its series of
interesting statistics relating to the fuel exports, market
and average prices, charterings, list of local coal mines
and managers, etc., and also contains the text of the
new wage agreements and legislation pertaining to the
coal mining industry. An account is also included of
the progress of local coal firms, such as the Ebbw Vale
Steel, Iron and Coal Company Limited, the Newport-
Abercarn Coal Company, and the Fernhill Collieries
Limited.

A Brief Memoir of James Robson. By James Robson.

45 pp. 8| in. x 6| in.; 19 illus. Birmingham : J.
Robson, Sandwell-road, Hands worth.

This pamphlet describes the part played by the
author’s father in the invention and introduction of the
two-cycle gas engine. The first engine, constructed in
1857, had a 3|in. cylinder of 6 in. stroke, the charge
being exploded at each revolution of the crank. A
3 horse-power horizontal engine was built in 1858-59, and
drove a circular saw for nine years, two others of the
same type being used on printing machines in North
Shields. In 1877 a patent was taken out for a two-
cycle engine, the pioneer of the type in which the front
end of the piston is used as a pump for dfaiving and
compressing the mixture of gas and air, and the back
end for the explosion or power stroke. Robson’s other
inventions included a gas forging hammer and a gas
pump, in which the return stroke of the pump piston is
effected by springs compressed during the explosion
stroke. He also experimented considerably in connec-
tion with a direct-lift aerial machine. The memoir is
interesting, as affording yet another instance of British
inventiveness in mechanical appliances which have
subsequently been adopted and elaborated by people of
other nationalities. The author informs us that he will
have pleasure in forwarding a copy of the memoir, free
of charge, to societies, etc., interested in the subject.

The second edition of the Magnet of Commerce, issued
by the Great Central Railway, is on the same high level
of interest and quality as the first, and contains the
latest statistics available at the date of publication.