THE COLLIERY GUARDIAN.

April 17, 1911.

850

flBflmiWMlI IM wmuui—t

astound people in this country. Nevertheless the
Bureau, by means of its researches in regard to
cables, motors and signals, has brought about some
improvement; in 1910, 79 men were killed by shock
or burns, or 0’11 per 1,000; in 1911, 87, or 0’12 per
1,000 ; and in 1912, 76, or 0’10 per 1,000.

To proceed to another branch of the Bureau’s
activity, the use of rescue and ambulance appli-
ances has made phenomenal progress. This no
doubt has been fostered by the “ boost ” in safety
that has arisen on the other side. The Bureau has
established six mine rescue stations, eight mine
rescue cars, and one rescue motor truck. In addi-
tion there are now owned and in use by 170 private
companies, 76 rescue stations, and about 1,200 sets
of apparatus ; mine operators own twelve and two
States own four rescue cars. There are now 31,203
miners who have been trained in the use of rescue
appliances, and it is stated that through the aid of
breathing apparatus the Bureau of Mines men have
rescued up to date 83 miners, whilst a large number
have been rescued by others. Three miners in the
employ of the Bureau have lost their lives within
the past two years while using breathing apparatus,
and a large number of men in the employ of mining
companies have perished in efforts to rescue others
in time of disaster. These figures cannot very well
be considered, failing the possession of the facts.
In many cases miners rescued by men wearing
rescue appliances might also have been saved by
men unprotected by apparatus; on the other hand,
men wearing apparatus have at times lost their lives
from causes that cannot justly be laid to the charge
•of the apparatus itself.

As we have already stated, the work of the Bureau
has been restricted by the lack of men and facilities,
and, therefore, there are some researches on other
subjects that still remain in abeyance. Such, for
•example, are those relating to falls of roof, the
investigation of safety appliances in connection with
mine haulage and hoisting, safety signalling systems,
mine fires, their causes and prevention, electric
•currents as possible causes of coalmine explosions,
mine ventilation and its relation to health conditions
in mines, the development of new types of metal-
mining explosives without poisonous fumes, mine
sanitation, &c.

The investigation in regard to falls, it is calculated,
would alone absorb from 35,000 to 40,000 dols. a
year for several years—a sum, however, which is
insignificant when we consider that, taking an average
compensation rate of 3 dols., the labour loss to the
•country from this one cause has been more than
15,000,000 dols. in five years, without including non-
f atal injuries. It is stated that the companies that have
been most successful in reducing accidents from falls
of roof have been those employing sufficient foremen
to enable the miners to be visited in their working
places two or three times a day. The assistant
foreman tests the roof, teaches the miner to do so
properly, and when a prop is necessary or a piece
must be taken down, waits in the place until the
work is done. This supervision is supplemented by
lantern-slide lectures at evening meetings, showing
how accidents occur and how they may be avoided.
In this connection, passing reference may be made
to the value of the cinematograph ; considerable use
has been made in the United States of the “ moving
picture ” to show the genesis o£ accidents, the
methods of setting props, &c., as well as the
administration of first aid.

In the Bureau itself a study is being made of mine
props, and numerous tests have already been
undertaken to determine the strength of various kinds
of timber, concrete pillars, and other types of roof
support. Work on a much larger scale is planned.
■Quite another branch of investigation awaits the
Bureau. A preliminary estimate, based upon limited
enquiry and examination, indicates an annual waste
or loss of coal in mining and handling of not less
than 250,000,000 tons per annum. This represents
a loss from the best and most easily mined coals
and those nearest the great centres of industry.
What is needed in connection with this loss, says
Dr. Holmes in his report, is a thorough under-
ground survey and examination at certain care-
fully - selected areas in each of the important

coalfields of the country, with a view to determining
the exact conditions under which mining operations
take place and the possibilities of adopting less
wasteful methods. It is estimated that an annual
expenditure of 50,000 dols. over several years would
result in a saving of considerably more than
50,000,000 tons of coal per annum.

In the fuel branch, investigations have been made
to determine the effect of different features of furnace
construction upon smoke production and efficiency;
in relation to the coking properties of coal, studies
have been made of the fundamental constituents of
coal and the possible improvements to be effected in
the utilisation of coke for foundry and other purposes.
A small by-product oven has also been designed for
the study of the precipitation of tar from the gas and
vapour from the oven by means of the electrical
method, which, it is said, promises much to the
by-product industry as regards lessened cost and
better separation of the by-products.

It is difficult to exaggerate the importance of this
great institution from a national point of view, quite
apart from its value to an industry that becomes more
cosmopolitan every day. All these researches
possess an interest to everyone engaged in coal-
mining and its derivative industries, and we some-
times regret that nothing has been done in the same
direction in this country. The British mining engi-
neer cannot be charged with any lack of initiative; in
the search for new methods of saving life and
cheapening production he has taken a great and
honourable part, but there are limits to personal
sacrifice, and the United States Bureau of Mines is
certainly an excellent agency for obtaining that
publicity without which many great endeavours are
wasted.

DICTILLATIM OF COAL II A VACUUWI *

It has already been shown that as the temperature of
distillation of coal is increased from. 500 to 1,100 degrees
the percentage of hydrogen in the gases evolved
increases, whilst the percentages of methane and ethane
decrease, a decomposition point, marked by a rapid
evolution of hydrogen, occurring at about 750 degs.
Below 450 degs. it was stated that “ ethane, propane,
and probably higher members of the paraffin series, form
a large percentage of the gases evolved.”

When coal that has been finely pulverised and
thoroughly dried in air at 107 degs. is exhausted at room
temperature, “ occluded ” gases in small quantity can
be pumped off. These gases, unlike the occluded gases
that can be obtained, sometimes in large volume, from
newly-won undried coal, consist largely of carbon dioxide
and carbon monoxide.

On raising the temperature of the coal during exhaus-
tion, the succession of events is as follows :—

Occluded or “condensed” gases (unextractable at
atmospheric temperature) continue to be removed in
small quantity up to 150 or 200 degrees. These gases
are mainly the paraffin hydrocarbons, the higher
members predominating.

At about 200 degs. there is a copious evolution of
water (small quantities of gas being also evolved), and
water continues to make its appearance at successive
stages in the distillation up to 450 degs., the highest
temperature employed in this series of experiments.
This water, as has been pointed out in a previous paper,
must be water of constitution. The gases evolved
during the period of most rapid formation of water con-
tain a high percentage of the oxides of carbon.

Between 200 and 300 degrees decomposition occurs of
some sulphur-containing organic compound, for the
gases evolved during that period contain a considerable
proportion of hydrogen, sulphide and tarnish mercury.
This decomposition, which begins at about 270 degs., is
practically completed at 300 degs. Simultaneously with
the hydrogen sulphide, the gases contain a considerable
proportion of the higher olefines, the evolution of which
does not, however, cease or fall off until a temperature
of 350 degs. is reached.

Liquids other than water begin to distil at about
310 degs., at which temperature a thin, reddish-brown
oil appears. There is no marked evolution of gas at
this temperature, and it seems probable that the oil is
not necessarily a product of decomposition, but may be
liquated out of the coal conglomerate.

A decomposition point occurs at about 350 degs.,
there being then a rapid evolution of gas, and much
viscid oil formed. Decomposition then continues with
increasing rapidity as the temperature is raised.

The mixtures of gases evolved at the different
temperatures are very complicated, containing, as they
do, hydrogen sulphide, carbon dioxide, ethylene, and the

* From a paper published in the Journal of the Chemical
Society, by Messrs. M. J. Burgess and R. V. Wheeler.

higher olefines, carbon monoxide, hydrogen, and the
paraffin hydrocarbons up to and including pentane.

The presence or absence of benzene vapour could not
be definitely established owing to the difficulty there is
in estimating it separately from the higher olefines ; but
neither benzene nor its homologues could be detected in
the liquid products of distillation in a vacuum up to
450 degs., so that the presence of the vapours amongst
the gaseous products is extremely doubtful.

Of the paraffin hydrocarbons, besides methane and
ethane, propane and butane were isolated by fractiona-
tion with liquid air and solid carbon dioxide dissolved in
ether, and the presence of petane established by explosion
analysis.

The higher paraffins mostly appear at the lower
temperatures of distillation, the range 100 to 300
degrees being attended by the greatest percentage
evolution. Above 350 degs., the decomposition point of
part of the coal substance, the percentage of methane
increases, and that of the higher hydrocarbons decreases.

It is conceivable that the paraffin hydrocarbons
obtained by exhaustion from coal at temperatures
between 200 degs. and 300 degs.—that is, below the
decomposition point observed—are present as such in
the coal, being held in a manner similar to, but more
forcible than, “ occluded ” methane at the lower tem-
peratures. The fact that there is a simultaneous
evolution of olefines, however, makes it more probable
that both classes of hydrocarbons arise from the thermal
decomposition of a solid paraffin or similar long-chain
compound.

One or two typical experiments only of the many that
have been carried out need be recorded. Several different
varieties of bituminous coal have been used, but no
important differences have been observed in their
behaviour on heating or in the products, whether
gaseous or liquid, of their decomposition. The com-
position of the occluded gases, it is true, varies with the
kind of coal and with its previous history (for example,
with the length of time since it was mined), but a study
of the occluded gases is but an incidental part of this
research, and has, moreover, already received the atten-
tion of numerous investigators.

The first experiment to be described was made with
a sample of Silkstone (bituminous) coal in the form of
fine dust, obtained by pulverising about 50 kilos, of
washed “ nuts,” and had been passed through a 240-mesh
sieve. The dust was not dried before use, and gave off
a considerable volume of occluded gases on exhaustion
at atmospheric temperature. When these gases had
been removed, the coal was heated to 100 degs.,
exhaustion being continued.

Gases Evolved at 100 Degrees.

The volume of gases evolved at 100 degs. amounted
to 34 cubic centimetres per 100 grammes of coal,
measured at N.T.P. Their composition was as follows:—

Per cent.

COo ....................... 6’70

Oo......................... 1’65

CoHt ...................... 0'85

CnH2n(u>2) ................ 1’30

CO ........................ 1*40

Ho......................... 1’90

CnH2n+2 .................... 84’55

Gases Evolved at 200 degs.

At 200 degs. 65’5 cubic centimetres per 100 grammes
of coal were collected. A complete analysis was made
of a portion of this gas, and the remainder passed into
a condensing apparatus surrounded by a solution of
solid carbon dioxide in ether, whereby a temperature of
about —80 degs. was obtained. A portion of the gases
(about 7'5 per cent, of the total volume evolved from the
coal at 200 degs.) liquefied at this temperature.

The analysis of the total gas evolved at 200 degs1.
was:—

Per cent.

CO2 ........................ 8’85

Oo.......................... 0'70

C2H4 .....................   0'85

CnH2n ...................... 2’90

CO ......................... 2-60

Ho.........................  2'75

CnH2n+2...................... 81'00

Gases Evolved at 300 degs.

The temperature of the coal was now gradually raised
to 300 degs. There was no further evolution of gas
until a temperature of about 270 degs. was reached; the
gases then evolved, tarnishing badly the mercury over
which they were collected.

Heating and exhaustion were continued during two
days, the temperature being maintained at 300 degs.
Towards the end of the heating the gases evolved ceased
to tarnish mercury. Altogether, 58 5 cubic centimetres
per 100 grammes of coal were collected.

Butane was isolated from the gases by liquefaction, as
in the case of the gases evolved at 200 degs. The analysis
of the total gas evolved showed:—

Per cent.

COo and HoS............... 35'35

C2H2 .................... 0'55

C2Hi .................... 1'05

CnH2n .................... 18'85

CO ....................... 10'50

H2 ..................... 13'35

CnH2n+2 .................. 18'85	.

Decomposition of some part of the coal substance had
obviously taken place between 270 and 300 degrees,
for although the volume of gases evolved was not large,
their composition was very different from that of the
gases evolved below 200 degs.

Gases Evolved at 350 degs. and at 400 degs.

On raising the temperature of the coal above 300 degs.,
a rapid evolution of gas took place between 320 and
350 degrees, and, after maintaining the temperature
during 8 days at 350 degs., 985 cubic centimetres of gas
per 100 grammes of coal were collected. The tempera-
ture of the coal was then gradually raised to 400 degs.*,