May 19, 1916.

THE COLLIERY GUARDIAN.

947

The inflammable gases which could accompany
methane in firedamp, through circumstances which are
fortuitous or little understood, are ethane, ethylene, and
hydrogen. None of these gases produces any appreci-
able retardation of the flashing point, so that it would
be easy to. study their influence on firedamp by pre-
paring mixtures of each of them with methane in
different proportions and seeking to inflame them with
metallic wires of a diameter which would be incapable
of igniting methane alone.

From the conclusion that the most oxygenated mix-
tures are the most easily inflamed, the author always
attempted in his experiments to maintain mixtures close
to the lower limit of inflammability, without, however,
always accomplishing it. He has obtained the following
results, which he considers as simply a step in advance,
but which give an idea of the influence exerted by the
presence of other gases on firedamp mixtures.

Of ethane, whose limit of inflammability was 3-9, the
author employed 4-5 parts with 1-82 parts of methane,
in order to accomplish inflammation by the fusion of a
ferro-nickel wire of 0-3 mm. diameter. In this case the
volume of ethane was 66 per cent, of the total volume
of the two inflammable gases.

Of ethylene, whose limit of inflammability was 3*6, he
used 4 parts with 2-85 parts of methane to obtain inflam-
mation under the same circumstances. In this case
the ethylene was 58-5 per cent, of the total volume of
the two inflammable gases.

Of illuminating gas, with a limit of inflammability of
S’5, he obtained ignition by using 5 parts mixed with
4’5 parts of firedamp, the illuminating gas being,’ there-
fore, 54 per cent, of the volume of the two inflammable
gases.

• Hydrogen and methane gave ignition with a mixture
containing 2-9 parts hydrogen and 6-1 parts firedamp,
the hydrogen therefore representing 32-2 per cent, of
the total volume of the inflammable gases.

Thus we see that a large quantity of the foreign gas
is necessary to cause methane to lose Its retardation of
flashing point under the conditions existing in these
experiments. This does not prevent a relatively small
quantity of these same gases from extending the limits
of inflammability of firedamp mixtures, but it is interest-
ing to note that methane conducts itself in this case like
a true paraffin in diminishing the sensitiveness of the
inflammable mixtures, as is the case with gun cotton
impregnated with paraffin which requires a much
stronger detonator to detonate it than if it were in the
dry state.

The relatively large quantity of these gases, which it
is necessary to add to pure methane to render it inflam-
mable by means of a thin metallic incandescent wire,
proves that the presence of traces of hydrogen or of
ethane reported by chemical analysis would not have
any appreciable influence on the characteristic properties
of firedamp. In any event, this natural gas should not
be protected by a “ sacred taboo,” which would take
away the value from experiments made with methane
sufficiently pure, and which can be prepared at a low
net cost by a method which will be indicated later. On
the contrary, the possible influence on the properties of
natural firedamp in fuel gases of hydrogen and oxide
of carbon should be taken into account.

(5) Influence of Inert Gases on the Properties of
Firedamp Mixtures. — The influence of nitrogen and
carbonic acid on the limits of inflammability of methane
is only appreciable as the diminution in the proportion
of oxygen is felt. The author’s experiments, in accord
with those of Le Chatelier, show that each 1 per cent,
of carbonic acid added to the air up to 8 per cent, raises
the lower limit of inflammability by about -y oTo o • But
the case is a little more complex in mines where the gas
coming from the operation of gobbing produces an
enrichment of the air in the mines in carbon dioxide
and water vapour at the expense of the oxygen of the
air. The upper limit of inflammability descends rapidly
and the lower limit is raised slowly in direct ratio, as the
content in oxygen is diminished, until we have only a
single value toward 13-5 per cent, of oxygen with a
content of 6-7 per cent, of methane.

There is stifl another interesting point to. note, namely,
the influence of carbon dioxide on the diminution of
the rapidity of combustion of firedamp mixtures, of
which it forms a part, and from which one can draw
material for useful deductions. As noted by F. Clowes,
the composition of air when it leaves the flame of a
candle or of an oil or alcohol lamp is comparable to that
exhaled from the lungs. Now, since the gas from gob
areas is also the result of a slow combustion, it is easy
to see that the air exhaled from the lungs could be
substituted in the laboratory in experiments with fire-
damp, of which those which follow have a special
interest.

Let us now consider the re-lighting, without danger,
of safety lamps in a firedamp atmosphere.- The
re-lighting of safety lamps in a mine has been the cause
of many discussions, and Marsaut has said relative to
materials for re-lighting by friction, which are considered
the safest to-day (as based on the experiments at
Frameries on this subject) :—

But for those (re-lighters of white phosphorus) the
experiments at Frameries and elsewhere do not give
the certainty that the lamps submitted to the proof
were completely freed from inert gas before the
re-lighting. At Frameries prompt re-lighting wire
gauze made red hot or very warm especially occupied
attention, but under these conditions could one be
sure that the lamp is free from all inert gases of
former combustion at the moment of re-lighting?
The very capricious results of the tests allow one to
doubt, or even to think, the contrary.

The non-explosive phosphorus re-lighters which are
supposed to be almost inoffensive, were not submitted
at Frameries to a sufficient number of tests to lead
to a sure conclusion.

In consequence of the above, the author is led to
believe that, if we could assure ourselves that the atmo-
sphere of the lamp at the moment of re-lighting was
under the same conditions as when we studied this
re-lighting, the problem would be solved. Now, the
gas exhaled from the lungs mixed with firedamp
diminishes considerably the latter’s rapidity of combus-
tion, which becomes comparable to that of mixtures near
the limit of inflammability. Then, if in a safety lamp
which has been extinguished some time, and which no
longer contains inert gases of combustion we inject air
from the lungs, one would then be able to fill the lamp
with a firedamp mixture which is inflammable,-but onlv
feebly explosive, and non-capable of propagating the
flame from the exterior.

After that it would be easy to judge the effect of the
exhaled air on the combustion of a safety lamp by blow-
ing softly on the top, an operation which could be
executed with very little practice. From another point
of view, the author has been able to observe with an
acetylene safety lamp 'different phases of the extinction
of firedamp mixture through its impoverishment in
oxygen and its mixture with residual gases of its own
combustion, by working as follows :—To make this
experiment, he used a lamp of the Tombelaine system
with low admission, which permits the flame to be
reduced at will, to examine the aureoles. If now,
having reduced the flame to merely a luminous point,
we introduce the lamp under a glass bell of about 15 to
20 litres capacity, half-filled with methane or
firedamp, and gradually raise the lamp, we see
the aureole first elongate and the inflammation
en masse of the gas contained within the gauze.
But instead of seeing the flame extinguished—
as would be the case of an acetylene flame thrust into
an atmosphere which contained 12 per cent, of oxygen—
we see the gas first ignite and then become extinguished
at the wick; then, as the air entering at the bottom of
the lamp dilutes the products of combustion, we see the
acetylene flame form a newT aureole which is elongated
in its turn with ignition, and new extinction of the fire-
damp mixture in the same manner as before; and thus
we could repeat the same thing several times, if desired.

These experiments allow an answer to be made to a
question often asked by mine foremen, namely, wThy one
sometimes sees firedamp suddenly ignite in the interior
of lamps, accompanied by an explosion, while at other
times there is formed only a very much elongated
aureole without sudden extinction. The answer is easy :
If the air of the mine is pure, its mixture with firedamp
is at first explosive, but, if the air of the mine is rich
in blackdamp, as the residual from respiration or from
its mixture with g'as from gobbing, the aureoles are more
or less elongated and the inflammations in the interior
of the lamp do not become true explosions. Probably
an extension of these considerations would .give us an
explanation of “ sharp gas.”

Pure Methane from Commercial Aluminum Carbide.

Admitting that the properties of firedamp as an
inflammable gas could be studied starting with pure
methane, there still remains to be explained the method
of preparing this gas under conditions of purity neces-
sary to this end, and at a price sufficiently reasonable
for the purpose.

Earlier workers have not made sufficiently clear the
fact that methane prepared by means of the acetate
often contains unsaturated hydrogen and hydrocarbons,
and that prepared by means of the commercial
aluminum carbide may contain considerable quantities
of hydrogen, especially if it is produced hot. It
remains to find other means to purify the gas, which
would require a second operation, or to employ pure
carbide of aluminum prepared by the Moissan process,
costing 400 fr. per kilog. This would make 1 cu. m. of
pure methane at 0 deg. Cent, and 760degs.. pressure.
For these reasons the author has undertaken another
investigation, in which he succeeded in preparing pure
methane by means of commercial aluminum carbide.

The principal impurities of aluminum carbide are the
carbides of calcium, iron, and silicon, together with an
excess of aluminum and uncombined carbon and of
alkalies, with a little aluminum sulphide, and perhaps
aluminum silicide.

The carbides of aluminum and of silicon are not
attacked by cold water, so that we are not handicapped
by their presence. As aluminum carbide is only
attacked slowly by cold water, the problem resolves itself
into the separation of the carbides of calcium and the
alkalies by a simple treatment with cold water, provided
the hydrates of lime and alkali liberated by this reaction,
and which remain enclosed in granules of aluminum
carbide, do not later act on the metallic aluminum pre-
sent in excess, and produce hydrogen, because it is this
gas mixed with methane which modifies most strongly
the properties of the latter gas. But even in the absence
of alkalies, aluminum decomposes water slowly, by
virtue of the following thermic equation :—

Al2 + 6H2O = A12O3.3H2O + 3H2 + 186 calories.

This reaction is more easily disturbed - if the aluminum
contains traces of calcium or alkali metals. On the
other hand, the reaction once commenced will be imme-
diately lessened in rapidity on one side by a slight layer
of aluminum hydrate which covers the metal, and
especially by the presence of little bubbles of hydrogen
which cover it. These are easily disengaged either by
heating or by forming a vacuum above the liquid. By
taking note of the different facts wrhich the author has
discovered, he has deduced the following method for the
purification of carbides :—

It is necessary first to take out the excess of
aluminum, and this can easily be done by pulverising
the carbide between the cylinders of a rolling mill,
which, at the same time, flattens out the metallic
aluminum. It then only remains to sift the mixture, to
separate the good part from the metal.

To get rid of the calcium carbide, the sifted aluminum

is treated several times with water until the supernatant
water is clear. As the aluminum hydrate is only slightly
soluble in water we transform it into a very soluble
chloride by means of washing with dilute hydrochloric
acid. For this purpose use 5 per cent, of acid of 1-19
specific gravity, then continue washing with water until
the wash water no longer is acid. For 50 grammes of
carbide we would require about three washes with
500 c.c. of water before the treatment with acid, and as
much again afterwards.

After this purification, the carbide is in condition to
be used, but one should also add the precaution of
rapidly drying by carrying off the water by means of
alcohol, followed by one washing with ether.

In order to obtain from this carbide a methane almost
free from hydrogen, it is necessary to avoid as much as
possible the disengaging of little bubbles of hydrogen
which cover the aluminum during the attack on the
carbide. This can be done by giving a certain thick-
ness to the mass of carbide on the bottom of a conical
flask where the reaction is produced. If, on the other
hand, we give a certain height to the water which the
gas has traversed to reach the gasometer, one will then
find it in its best condition, and one can obtain in winter
(with the temperature about 14 degs. Cent.) a methane
almost free from hydrogen (about 0-2 per cent.).

But this process becomes incomplete in summer, when
sometimes the author has found ifi the methane as much
as 8 per cent, of free hydrogen. It is easy to- see that
under these conditions the liquid has become alkaline,
its analysis showing it to contain aluminate of soda.

To prevent this occurrence, it is sufficient to- replace
the water which covers the carbide by washing daily,
until the wash waters are no longer alkaline. Operating
thus, we can obtain even in summer methane containing
less than six parts per 1,000 of hydrogen, which is avail-
able for the greater part of the experiments. For the
work of analysis, it suffices to purify the gas by washing
it with potash, and passing it through a tube containing
palladium.

THE MINING ASSOCIATION OF
GREAT BRITAIN.

Coal Production.

An important conference on this question took place
at the Westminster Palace Hotel, London, on Tuesday
last, between the Parliamentary Committee of the
Mining Association and the executive of the Miners’
Federation of Great Britain. Mr. Adam Nimmo, presi-
dent of the Association, occupied the chair, and Mr.
Robert Smillie, president of the Federation, the vice-
chair.

The principal matters discussed had reference to
absenteeism, suspension of the Eight Hours Act, boy
labour in mines, women labour, and employment of
workmen after the war.

The Mining Association was represented by the under-
named, in addition to the president :—Sir Lindsay
Wood, Bart., R. W. Cooper, John Morison, Col. W. C.
Blackett, Ridley Warham, Arthur F. Pease, and
Reginald Guthrie (North of England); Tom P. Martin
('Cumberland); W. Russell, C.B., James M. Strain,
J. T. Forgie, Robert Baird, James A. Clark, James
Borland, Charles Carlow, and A. H. Crichton (Scotland);

F.	J. Jones, F. Parker Rhodes, R. Richardson, J. F.
Warrington, C. B. Crawshaw, Percy C. Greaves, and
Roslyn Holiday (Yorkshire); H. Eustace Mitton, George
J. Binns, Henry Stevenson, and Leslie A. Wright (Mid-
land Counties); Sir J. S. Harmood Banner, M.P., Sir
William Barrett, Sir Henry Hall, I.S.O., W. H.
Hewlett, Charles Pilkington, and A. M. Lamb (Lanca-
shire); Col. A. H. Heath and J. Selby Gardner (North
Staffordshire and Cannock Chase); Sir Francis Brain and

G.	E. J. McMurtrie (Dean Forest and Somerset); Fred
L. Davis, Joseph Shaw, K.C., Evan Williams, T. H.
Deakin, Hugh Bramwell, and Finlay A. Gibson (South
Wales); and Sir T. R. Ratcliffe-Ellis, law clerk and
secretary. After a long discussion, an adjournment to
enable each side to consider the points which had been
brought forward, and a further conference, the following
resolutions were unanimously adopted :—

(1)	That, in regard to- absenteeism, this meeting
agrees to the matter being referred to the districts, on
the distinct understanding that committees will be at
once set up in each district to devise and put into
operation effective machinery to secure the attendance
of all the workmen employed to the fullest possible
extent, and to enquire into the circumstances of work-
men employed at the mine not being provided with
work when they have presented themselves at the
mine, the intention being to secure, as far as possible,
the output of coal necessary for the country’s needs;
and that this joint meeting be adjourned to Thursday,
June 22, to receive reports of progress from each
district.

(2)	That the subjects of the suspension of the Eight
Hours Act, the working of one hour extra on 60 days,
and employment of boys above and below ground, be
considered at the adjourned meeting.

(3)	That this joint meeting recommends to the
several districts that the periods of the recognised
holidays be curtailed as far as possible, in view of the
urgent national necessity for an increase in the output
of coal.

The late Mr. M. Fowler, Northallerton, chairman of the
Malleable Iron and Steel Company, left T50,375.

We understand that, in consequence of the further exten-
sion of the already very considerable plant owned by the
Newcastle Electric Supply Company Limited, Messrs. R. H.
Longbotham and Company Limited, of Ings Foundry, Wake-
field, have purchased the existing sets of Parsons’ turbo-
generators, with the condensers, etc., ranging in capacity
from 2,500 to 5,000 kw., which are being replaced by units
of much higher capacity.