October 11, 1918.

THE COLLIERY GUARDIAN.

765

CURRENT SCIENCE

The Use of the Interferometer in Gas Analysis.

The Rayleigh interferometer (Technical Paper 185,
Bureau of Mines, Washington), makes use of the
optical properties of gases, and is suitable for
analysing a binary gas mixture. The instrument is
made in two different types, viz., a laboratory model
with gas chamber, a metre in length, which is capable
of giving results accurate to within 0-20 to 0-03 per
cent., and a short or portable type where less accu-
racy is desired. The manner in which interference
bands are produced is explained, according to the
theory of Young, and it is shown that, other things
being equal, the accuracy of the measurements
depends entirely on the length of the gas chambers.
The greater the difference of the coefficients of abso-
lute refraction in the gases employed, the greater
is the accuracy of the method. The mode of con-
ducting a test with the apparatus is described, and
the way in which the readings are taken is set forth.
It is stated that complete mastery of the instrument
comes only from considerable experience. A number
of results of experiments are recorded. These relate
to mixtures of carbon dioxide and air and mixtures
of methane and air, and they show the effect of
lowering the oxygen contents of samples of air, which
then contain less oxygen and more nitrogen. Tests
also show methane and air with lowered oxygen con-
tent. A calibration of the interferometer is given
for oxygen-nitrogen mixtures, with graphic diagrams
to explain results. An illustration is furnished of
an apparatus for producing pure oxygen and
hydrogen by means of electrolysis, and as a further
help in the use of the instrument a table is appended
of the absolute indices of refraction of various gases
at 0 deg. and 760 mm. pressure.

Measuring Heat Losses at the Chimney.

M. Chopin (Comptes Rendus) describes an instru-
ment which records simultaneously the value of
temperature and carbonic acid gas content of the
smoke and the resultant loss -at the chimney. If P
is the percentage loss of calorific power of the fuel,
and Tj and T2 are respectively the temperature of the
air when entering the grate and of the smoke when
passing the receiver of the apparatus; further, if A
is the quantity of CO2 in the smoke, these

T — T
factors are connected by the relation P = K ’

K being a coefficient of proportionality. In the appa-
ratus the temperature and percentage of CO2 are
represented by two electric currents, of which the
strength depends on these variables, the chimney loss
being obtained by dividing the value of these currents
as in equation. The electric equivalent of the CO2
content is arrived at as follows: When a constant
volume of the gas to be analysed is mixed in a con-
stant volume of a titrated solution of caustic soda,
a mixture of soda and carbonate of soda results, the
relative proportions of which depend on the CO2
content. Now the electric resistivity of a carbonate
of soda solution is three times as great as that of the
caustic soda solution from which it is derived. . It is
only necessary, then, to compare the electric re-
sistance of the solution before and after absorption
of the CO2 in order to arrive at the percentage of this
gas in the sample examined. The author gives a
rough illustration of the apparatus, which comprises
a pyrometer, a moving coil ammeter giving the per-
centage of CO2. The quotient of two currents is
obtained by referring the overlap of two pointers to
curves of equal loss at the chimney. A receiver is
used for (1) measuring a constant volume of soda
taken from a glass vessel; (2) mixing the CO2 and
the soda; (3) forming a resistance column of solution
between two electrodes forming part of the measuring
circuit. Tests made with the instrument show that the
method is sufficiently accurate for industrial purposes.

Composition of Refractory Silica Bricks.

Mr. J. S. McDowell (Engineering and Mining
Journal) attributes the tendency of silica bricks to
spall to the fact that temporary or true thermal ex-
pansion occurs largely over a narrow range of
temperature. Bricks made of Medina quartzite from
Huntingdon County, Pa., were subjected to eight
and ten burnings respectively. Expressed in per cent,
by volume, their mineral compositions were: . After
eight burns: Silicates 14, cristobalite 33, tridymite
53 per cent; after ten burns: silicates 11, cristobalite
28, tridymite 61 per cent. These results, together
with others obtained previously, are shown graphi-
cally. The percentage of “ quartz plus silicates”
reaches an approximately constant value of 13 per
cent, after the third burn, and probably the whole
of this 13 per cent, represents silicates formed by the
lime used as bond and the impurities in the raw
material. A completely inverted brick should contain
about 87 per cent, tridymite and 13 per cent, sili-
cates. Apparently 16 or 17 burnings, or one con-
tinuous burning for a month would be needed to reach
this composition, so that the cost is prohibitive.

So far as permanent expansion is concerned, there
is little advantage in more than one burning, and for
practical purposes none after the third burning. A
silica brick made of Baraboo quartzite contained:
quartz -plus silicates 67 per cent., cristobalite 27 per
cent., tridymite 6 per cent. ; a brick of Medina
quartzite contained: quartz plus silicates 25 per
cent., cristobalite 71 per cent., tridymite 4 per cent.
The difference is attributed to differences in the tex-
ture of the quartzites. The Baraboo quartzite, being
much coarser in grain than the Medina quartzite,
cannot invert so rapidly.

Whilst considering Wernicks and Wildschrey’s
statement that ordinary quartzites do not produce
good silica bricks as too sweeping, the author con-
firms their general conclusion that the finer grained
quartzites with a cement of amorphous silica are the
most suitable for making bricks. He also confirms

AND TECHNOLOGY.

their statement that the selection of rock of the proper
texture offers greater possibilities for the production
of the best (tridymite) bricks than any alteration in
the process of manufacture. A coarse texture to
brick spalls less than one composed of fine grains, but
insufficient grinding may induce other defects. As
there are often wide variations in the textures of
quartzites of the same geological location, the
averages of a sufficiently large number of grain size
measurements should be taken.

Purification of Coal Gas by Electricity.

The deposition of tar and other impurities from coal
gas is described in Elektrotechnische Rundschau
(abstracted in the Electrical Review). High-tension
direct currrent is discharged between a cage made
of thin wires and a tube, the system of wires being
mounted in the middle of the tube. The gas is cleaned
in its passage through the tube. The tendency to-
wards the production of harmful discharges is least
if the wire electrode is negative. The shape of the
electrode is very important, and the sustaining insu-
lators are specially formed and cemented into the tube.
A | in. gas tube is passed through a series of cast iron
discs, between which the thin steel wires are fixed.
The whole arrangement is then placed in a felt-covered
tube, which constitutes the earthed electrode.

The apparatus was tested with a flow of 7,500 cu. m.
of gas per hour, two precipitation chambers of m.
height and 0-2 m. diameter being used. The discs
of the active electrode were of 100 mm. diameter,
and were fitted with 16 thin piano steel wires. The
passage traversed by the gas was about 4 m. long.
The gas was exposed to the discharge for about 0'4
second. After five hours’ operation the tar deposited
on the insulators was found to interfere with the
action. For complete cleansing of the gas 0’2 kw.
hour was required for 7,500 cu. m. of gas. The total
cost of the apparatus was about 2,000 marks. The
test was made with 20,000 volts and a current of about
3 milliamperes. The temperature of the coal gas has
little influence on the operation. Tar deposited at
175 degs. Fahr, is free from water and suitable for
asphalting. It can be cleansed in a washing appa-
ratus, and the residue of naphthalene can be won by
a second electric precipitation. The illuminating and
heating capacity of the gas is improved if the tar is
removed hot.

MANCHESTER GEOLOGICAL AND
MINING SOCIETY.

ANNUAL MEETING.

The 80th annual general meeting of the members of
the Manchester Geological and Mining Society was
held on Tuesday last at the rooms of the society,
Queen’s Chambers, John Dalton-street, Manchester.
Mr. Wm. Pickup presided.

The following gentlemen, having been duly
nominated, were elected:—Members federated: C.
H. Bolton, 1, Meanley-road, Astley, near Manchester;

E.	Hughes, Ynystowyn, Portmadoc, North Wales;

F.	S. Sinnatt, Great Clowes-street, Broughton, Man-
chester. Associate members federated : C. Croasdale,
Rose Mount, Coppull, near Chorley; H. Foster, 17,
Silverwell-street, Bolton; R. James, 6, Llantwit-road,
Treforest, Glam.; H. Maden, The Bungalow, Sharwey-
ford; R. E. Pritchard, Baigens Chawton, Alton,
Hants; D. C. Smith, The Lingards, Astley, near Man-
chester ; A. Stephens, 7, Cwm Terrace, Cym, Newport.
Associates federated: A. Cochrane, Peak House, New
Mills, near Stockport; E. H. Thomas, Elim Villa,
Alien-street, Mountain Ash, Glam.; T. Watkins,
Cartrefle, Rhondda-road, Ferndale, Glam. Student
federated: T. Jones, 167, Longfield-road, Bolton.

Council Report.

Mr. Sydney A. Smith (hon. sec. pro tent.) pre-
sented the report of the council for the year ending
July 31, 1918, in which it was stated that ten new
members had been elected during the past twelve
months, four members and six associate members,
both class federated. Twelve members had been trans-
ferred ; two students to associates, four associates to
associate members; two non-federated to associate
members, three to members and one to honorary
member. Sir Henry Hall, I.S.O. (past president) had
been elected an honourary member and two members
had become life members. There had been 12 with-
drawals of members by resignation and other causes
during the year, in addition to four deaths. The
membership now totalled 398. The following colliery
companies, in response to the appeal of the council,
had been added to the list of subscribers. The Swan
Lane Collieries Limited, the Westhoughton Coal and
Cannel Company Limited, the Bickerstaffe Collieries
Limited, William Ramsden and Sons Limited.

The council had to record with regret the deaths
during the session of: Prof. Edward Hull, M.A.,
F.R.S., who had been an honorary member since
1874; Mr. Thomas Ashworth (member), elected in
1878; Mr. W. A. Ritson (member), elected in 1897;
Lieut. Ernest Philips (associate member), killed on
active service.

Several additional members had joined his
Majesty’s Forces during the year, and in addition to
the nine members who had lost their lives in the ser-
vice of their country there were at the present time
over 70 members of various classes on active service.

Awards and Distinctions.

The following awards and distinctions had been
conferred on members during the year: Sir Thomas
Holland, K.C.S.I.; Lieut.-Col. Lionel E. Pilkington,
C.M.G.; Lieut.-Col. Chas. Godfrey Jones, D.S.O. ;
Major Harry La Trobe Campbell, D.S.O.; Capt.
Hubert Scholes, M.C.; Mr. W. T. Anderson, a member
of the council, was last year appointed by the Board
of Trade as special commissioner to Spain to inves-

tigate and report on the possibilities of the iron, steel,
and engineering industries in that country.

The Committee on Mining Education had met on
various occasions, and hoped to issue a report in the
near future.

The Committee on Lancashire Coalfields Research
was continuing its work.

Miss T. Vera Martin, in memory of her father, the
late Mr. J. S. Martin, had presented to the society a
most valuable collection of ordnance maps and docu-
ments, including a complete bound set of the “ Mines
Reports by the Government Mines Inspectors” from
vol. i. (1850) to vol. xlv. (1896) and a complete bound
set of the “ Mineral Statistics,” published by the
Government, from vol ii. (1883) to vol. xv. (1896).
The deceased was an old member of the society, for
some years was a member of the council, and honorary
secretary for a short period. He was his Majesty’s in-
spector of mines in his district for many years.

The financial position of the society was satisfactory,
considering the demands made on it through the war.

The society’s representatives on the council of the
Institution of Mining Engineers for the year 1918-
19 were as follows: Vice-presidents, Messrs. Wm.
Pickup and A. J. A. Orchard; councillors: Messrs.
W. T. Anderson, J. Ashworth, John Gerrard, Tom
Stone, Sydney A. Smith, and Clement Fletcher. The
balance sheet and statement of accounts was read by
the treasurer (Mr. Ashworth).

The Chairman, in moving the adoption of the report
and balance sheet, said a new students’ association
had been inaugurated which, when it got into full
working order, would be established in all the large
mining centres of the county, and would prove a
valuable auxiliary in obtaining new student members.
It would lead students to continue their studies and
finally reach the highest branches of the profession.

The report and balance sheet were adopted.

Election of Officers.

The following officers were elected: Vice-presidents,
Messrs. Vincent Bramall, J. Tardif Browne, William
Ollerenshaw, Tom Stone. Other members of the
council: Messrs. W. T. Anderson, H. S. Atherton,
N. O. Dixon, C. Fltcher, Geo. H. Hickling, R. Land-
less, S. C. Laws, J. D. Paton, A. Rushton, F. A.
Ross, F. N. Siddall, S. A. Smith. Hon. treasurer,
Mr. John Ashworth. Accountants, Messrs. Jones,
Crewdson and Youatt. Hon. secretary, Mr. N.
Williams,

The Chairman observed that Mr. Williams was now
with the Forces, but in his absence the work would be
done by Mr. Sydney A. Smith, who was elected acting
hon. secretary.

The Chairman said it was the unanimous recommen-
dation of the council that Mr. A. J. A. Orchard be
elected president of the society for the next twelve
months. He was one of their most valued members,
having joined the society in 1891, and had been on
the council for many years, sparing neither time nor
trouble where the interests of the society were con-
cerned. He would bring a sqund and large experience
and clear judgment to bear upon the business. It
was with the greatest pleasure that he moved Mr.
Orchard’s election as president.

Mr. Ashworth seconded the motion, which was car-
ried with acclamation. The chair was vacated by
Mr. Pickup and taken by Mr. Orchard.

The President said he appreciated the honour done
to him, and only regretted that his election was due
to the fact that Mr. Pickup was retiring. It was
no easy task to follow a president who had proved
himself as capable as Mr. Pickup, but he hoped to
have his advice and assistance and the support of
the members, so that at the end of the year he might
leave the affairs of the society in as sound a position
as they were now. He wished to say a word on
a matter which was outside the agenda but was of
urgent importance at the present time. That was the
output of coal. Two main factors were concerned—
labour and machinery. He did not propose to say
anything on the labour side of the question, but the
machinery side, though secondary, was also of great
importance. Owing mainly to the calling-up of skilled
repairers out of the collieries, there had been a general
deterioration in the machinery, and breakdowns were
frequent. To obtain a new machine for replacement
or development a permit was required. Delay in
issuing those permits might be unavoidable—only
those who had to deal with competing priority claims
were in a position to say—but the point he wished to
emphasise was that delay in the supplying of essential
machinery meant a loss of output as surely as shortage
of labour. He moved a vote of thanks to Mr. Pickup
for his services as president of the society. He thought
Mr. Pickup’s influence would be felt for many years.

Mr. Stone seconded the vote of thanks, which was
carried unanimously.

In replying, Mr. Pickup said he regretted that
during his period of office peace had not been attained
in the war, and he hoped that satisfaction was in
store for Mr. Orchard.

Calorific Values and Ash.

Mr. Drakeley read a paper on “ Calorific Values
and Ash Yields of Coal Supplies from the Same
Seam ” (see p. 753).

Discussion.

The Chairman moved a vote of thanks to Mr.
Drakeley.

Mr. Laws asked whether Mr. Drakeley found by
experience that there was the same ash residue from
shale samples taken from different parts of the seam,
or did it vary to any extent? If it did it would affect
the accuracy of the equation given.

Mr. Drakeley replied that the shale certainly might
vary in ash. One must sample the shale as well as the
coal, and select the first samples to fix the line; in
other words, to take the average of the shale that was
likely to come to the surface with the mined coal. In