August 9, 1918.

THE COLLIERY GUARDIAN.

287

CURRENT SCIENCE

Recovery of Toluol at Gas Works.

The process of recovery as carried out at the Des
Moines Works (United States) is described by Mr.
C. Adams (American Gas Engineering Journal) as fol-
lows : The water gas, after purification, is passed
through scrubbers fitted with trays, where it is sub-
jected to a wash or absorbent oil. This oil absorbs
the benzine group from the gas, or, as usually ex-
pressed, the gas is “stripped.” The mixture of straw
oil and the benzine group, known as the benzolised
oil, is run off into a storage tank. It is then pumped
through the light-oil still system, where the tempera-
ture is so regulated that the lighter benzine group
vaporises and passes out of the still, through con-
densers, to a light-oil storage tank. The wash-oil, or
de-benzolised oil from which the benzine group has
been removed, is returned to the scrubbers. Another
pump keeps up a continual circulation of the oil from
the benzolised tank through one of the two scrubbers.
The scrubbing and the recovery of light oil is thus a
continuous process, scrubbing ceasing only when the
exhausters are shut down in consequence of the holders
being full. The light oil thus made is run into a
fractionating still having a capacity per charge of
1,600 gallons. Here, by means of cuts, the oil is
divided into its three main constituents—crude benzol,
crude toluol, and crude xylol. The vapours are dis-
tilled over from the still, still-column, planer, and con-
denser in the order named. Owing to the fact that
toluol overlaps benzol, and xylol overlaps toluol, there
are five products which, according to the nomenclature
adopted, are known in order of distillation as B,
BT, T, TX, and X. The B, or crude benzol, is stored
for enriching purposes, or for sale. The T, or crude
toluol, and X, or crude xylol, are stored for sale,
though xylol may be sometimes used for enriching the
stripped gas. The BT and TX oil, known as “inter-
mediates,” are put on one side until enough has accu-
mulated to make what is called a BT, or a TX run in
the fractionating still.

In the process of fractionating, the temperatures are
gradually raised till the benzol starts over—the heats
are held below 180 degs. Fahr., which is the benzol
cut—at the outlets of the planer. This is necessary to
keep the toluol from distilling over the benzol. The
oil is run directly to the benzol storage tank. When
the oil ceases to flow with the temperature of 180 degs.
the heats are gradually raised, and the oil diverted to
drums. The oil at this point is a mixture of benzol
and toluol, or BT. By watching the temperatures,
the second cut can be made when the oil which is being
distilled over from the planer shows a high percentage
of crude toluol. The cut between the toluol and the
xylol is determined in the same way. The crude toluol
and the crude benzol recovered per gallon of gas oil
amounts to 2-21 and 2*84 per cent.

Loss in the Manufacture of Ammonia Liquor.

In a paper on this subject before the annual general
meeting of the Society of Chemical Industry, Mr.
A. Marsden reports some experience * with a plant
of the Wilton type. The plant worked satisfactorily
as far as the quality of the concentrated liquor pro-
duced was concerned, but it soon became evident that
considerable losses of ammonia were taking place, the
efficiency of conversion from crude to concentrated
liquor being only about 80 per cent. As a result, the
plant was run under test for 24 hours, maintaining
as far as possible the usual conditions of working,
but taking careful readings and measurements. The
figures obtained showed that, of the total ammonia
supplied to the plant as crude liquor, 90-1 per cent,
was obtained as concentrated liquor. This improved
result was doubtless due to the increased and constant
supervision during the test.

The losses of ammonia in connection with a plant of
this type may be due to several causes. Desulphurisa-
tion, for instance, is a source of loss in the catch tower
in consequence of rushes of gas. In order to keep a
check upon the working of the tower, a thermograph
may be connected with one of the trays to indicate
whether ammonia is passing. Losses due to pumping
may attain considerable proportions, leakage being
caused by the pump rod being rapidly attacked by
the action of cyanides, and so developing a “ shoulder.”
Should the storage tanks become warm, ammonia
escapes from the bubbler unless the stream of water
is largely increased. Careful attention should there-
fore be given to the outlet temperature of the final
condenser.

Loading rail tanks is another source of loss amount-
ing on the average to 15 gallons of 25 per cent, liquor
per 10 ton tank. In order to avoid this loss, a pipe
should be permanently carried to the “bubbler,”
which should be fed with extra water during loading,
the rail tank being connected to the pipe by flexible
hose.

Frequent examination of the apparatus is neces-
sary, because small leakages readily develop into
large ones, and often become all the more difficult to
rectify. All gauge cocks should be moved daily, be-
cause if once fixed they readily break, being made of
cast iron. Careful warming up of the plant is one of
the best methods for preventing numerous small leaks
on the still and reflux condensers.

Purification of Coal Gas by Electricity.

The deposition of tar and other impurities from coal
gas has recently been undertaken by electric means,
and according to the Elektrotechnische Rundschau
satisfactory results have been attained. High tension
direct current 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. It is essential to
prevent access of air to the precipitation chamber in
order to avoid the danger of explosion. It was found
that the tendency towards the production of harmful
discharges is least if the wire electrode is negative.
The shape of the electrode is very important, and the
sustaining insulators are specially formed and

AND TECHNOLOGY.

cemented into the tube. A half-inch 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 consti-
tutes the earthed electrode.

The apparatus was tested with a flow of 7,500 cu. m.
of gas per hour, two precipitation chambers of 1| m.
height and 0-2 m. diameter being used. Discs of the
active electrode were of 100 mm. diameter, and were
covered 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 secs. 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.-hours were required for
7,500 cu. m. The total cost of the apparatus was about
2,000 mk. The test was made with 20,000 volts and a
current of about 3 milli-amperes. 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 wash-
ing apparatus, and the residue of naphthaline can be
won by a second electric precipitation. The illuminat-
ing and heating capacity of the gas is improved if the
tar is removed hot.

BOOK NOTICES.

High Explosives. By Capt. E. de W. S. Colver.
830 pp. + xxix. 9| x 6 in. 155 figs. London :
Crosby Lockwood and Son. 1918. Price £3s 3s. net.

The modern plan of treating the subject of high ex-
plosives as a separate entity, apart from that of explosives
generally, is doubtless convenient and necessary in view of
recent developments, but, as the author points out, a
rigid distinction is not always practicable, as many
explosives, not commonly termed high explosives, are
capable of acting as such under suitable conditions. In
this volume, however, the author has confined himself
strictly to those compounds about which no doubt can
exist, viz., the nitro derivatives of the aromatic series,
together with certain nitro-paraffin compounds of which
at pi esent no extended use has been made.

The treatment of the subject follows much the usual
lines, the evolution of high explosives being briefly out-
lined in the opening chapter, whilst considerable attention
is, first of all, devoted to their sources of supply and
the raw materials from which they are manufactured. The
latter section will be found particularly useful as con-
taining the very recent work on the evaluation of com-
mercial toluenes and other hydrocarbons.

The author, in his historical account of the evolution of
the high explosive, has fallen into a very curious error.
Dealing with the development of fulminate igniters, he
states that E. O. Brown in 1868 found that compressed
guncotton could be exploded by this means, whereas the
whole point of Brown’s discovery was that wet guncotton
could be exploded by a dry guncotton primer and ful-
minate igniter, which is a very different matter.

The broad principles underlying the process of nitration
are very clearly explained, and many useful data on the
concentration of the mixed acids and on the recovery of
the waste acid are included.

A fairly complete account is given of the properties of
the various nitro bodies used, either alone or as ingre-
dients of composite explosives, the sections on T.N.T.,
picric acid and the nitro-aniline derivatives being as. de-
tailed as present restrictions will permit, and the various
nitrating and purifying processes are explained by copious
diagrams and illustrations. The value of these sections
lies chiefly in the fact that they give, in a readily acces-
sible form, an excellent resume of the work carried out
on these explosives in Continental countries up to the out-
break. of war. Attention may particularly be called to
the table of colour reactions of nitro bodies, which should
prove a useful aid in identifying various explosives.

Considerable information is afforded on the less com-
monly used explosives, such as hexanitrodiphenylamine,
which should be of service to those working on the.compo-
sition of foreign or unidentified explosives, whilst the
section on the nitro-paraffins is a more or less new feature,
which is of interest in view of future developments.

A chapter on the uses and adaptation of high explosives
is included, but, for obvious reasons, the author has had
to tread very warily here.

A large section is devoted to the various means of
initiating detonation, the most useful portion of which will
probably be found to be the account of recent American
activities in this direction; but the author is decidedly
less happy when away from the subject of high explosives
proper, and both this section and the following one, dealing
with the theoretical consideration of explosion and detona-
tion, present no special features, and rather give the idea
of having been collected from readily available sources,
and added for the sake of completeness. No great grasp
of this portion of the subject is apparent, and some of
the facts are not altogether reliable. For example,
no one who has had any experience with fulminate will
agree that this material, as usually produced, is vrhite
to brownish-grey, as special means of bleaching have to
be adopted if white fulminate is required; whilst the state-
ment that the brownish-grey colour is probably due to
intermixed particles of metallic mercury in a fine state of
division is open to grave doubt.

Apart from these sections, however, the book is a
valuable addition to the literature of high explosives, and
the author is certainly to be congratulated, on haying
collected together a large mass of very useful information,
much of which has not hitherto been very accessible; and
from this point of view the book is likely to occupy a
high place, at the present time, as a work of reference.
One point mav, however, be raised. A book of this
character, published, say, early in 1915, would have sup-
plied a much-felt want, but after the lapse of nearly, four
years of unprecedented work on explosives, practically
none of which, for obvious reasons, is yet available for
publication, one cannot help but doubt whether the present
is really a suitable time for the production of a book on
explosives when much of the information may .be found
to be, comparatively speaking, out of date at a time which
it is hoped is now not far distant.

The ponderous and unwieldy character of the book,
comprising, as it does, 850 pages, is somewhat of a draw-
back. Unnecessarily large type, both for headings and
references, has been used, and a very uneconomical method
of arrangement has been adopted. The most striking
example of wasted space is the invariable use, in consti-

tutional formulae, of benzene rings fully an inch and a half
in length with the result that six of these are sufficient
to occupy a whole page. Far from adding to the clear-
ness, it is considered that these large formulae are actually
less convincing to the mind’s eye than those of the more
usual type. The subject matter itself is not wholly free
from a tendency towards unnecessary repetition, and it
should not have been difficult to have kept the book within
much more convenient limits without in any way detracting
from its undoubted usefulness.

The Journal of the Institute of Metals.	Vol. 19.

Edited by G. Shaw Scott, M.Sc. 316 pp.
8i in. x 5^ in. ; 9 plates. (The Institute of Metals.
London : 36, Victoria-street, S.W. 1.) Price 21s. net.

We are glad to see that, despite the war, which makes
it difficult to secure and publish much original scientific
matter, the editor of the Journal of the Institute of Metals
has been able to bring out the new half-yearly volume
of the Journal so promptly. Amongst the papers is a joint
contribution by the new president, Professor Carpenter,
F.R.S., and Miss C. F. Elam, on “An Investigation on
Unsound Castings of Admiralty Bronze : Its Cause and
the Remedy.” The printed discussion covers 46 pages, or
more than twice as much space as does the original paper
—a testimony to the interest taken in the subject.
Messrs. Rix and Whitaker’s paper on “ Aluminium Bronze
Die Casting” is likewise of interest to engineers and
metallurgists. Other valuable papers included in the
present volume are those by Mr. J. N. Greenwood, M.Sc.,
on “ The Relationship between Hardness and Constitution
in the Copper-rich Aluminium Copper Alloys ” ; by Dr.
Gulliver on “ Grain Size ” ; by Mr. E. O. Ellis, M.Sc., on
“ Lead-Tin-Antimony Alloys ” ; and by Mr. R. J. Ander-
son, B.Sc., on the “Annealing of Aluminium.” The
volume also contains the presidential address and a sum-
mary of recently published metallurgical information, as
well as an exhaustive index. The new Journal well
maintains the high standard that we have been accustomed
to look for in this valuable publication.

MINING ELECTRICAL ENGINEERING.

In the course of his reply to part of the comments
upon his paper (Colliery Guardian, May 31, 1918,
p. 1094), at the South Wales Institute of Engineers, on
July 26, Mr. Chris. Jones, M.I.E.E., Walsall, said
that, with reference to the request of Mr. Watkins and
Mr, Forrest for more information in regard to the
static condensers, he had not had the slightest trouble
with any of the sets since their installation. The switch
controlling the condensers from the bus bars was of
oil-immersed type, fitted with charging resistances on
the contact finger. The efficiency of the condenser at
ordinary frequencies and temperature could be safely
accepted as 99’5 per cent. The condensers were
made up of a specially selected tinfoil applied to
a very thin tissue paper. The dielectric consisted
of several layers of special interleaved tissue paper,
and the whole was immersed in best qualify oil.
They were built in units of about one microfarad—
the units being assembled in a strong, sealed me al case
in such number as were required to make up the total
microfarad capacity. The temperature rise did not
exceed 20 degs. Fahr. He (Mr. Jones) was glad to
inform the members that these condensers were now in
satisfactory use on 3,000-volt circuits—a fact which
should greatly assist engineers in improving the power
factor of their systems. Members would have noticed
also that lamps were used on the sets shown in the
paper, in order to dissipate the charge which might be
left in the condenser on switching off. The makers had
now designed a special oil switch, by which the con-
denser was switched on or off through these resistances.
As to the question of costs, the following might be of
use to some members:—To improve the power factor of
a 500 kilowatt load (working at 3,000 volts, 50 periods)
from 0’6 to 0*9, a capacity of 1,500 microfarads would be
required, having an output of 424 k.v.a. The cost
would be. £1350, complete with switchgear. If the
condenser was required to deal with a similar load, but
25-period instead of 50-period, its cost would be
approximately double, as the amount of capacity
required was inversely proportional to the frequency.
For a 600-volt circuit the cost was approximately the
same as for a 3 000 volt circuit. In the case of the
power factor of a 40-horse power motor working
at a load of, say, 33 kw. and a power factor of 0’5 to be
improved to 0 95, the capacity required would be 400
microfarads ani*the cost would be £50. If the motor
was working at a power factor of 0’65, a capacity of 240
microfarads would be required—price, £48. As a power
factor of 0’95 was higher than the usual specification,
the following might be of interest:—To improve the
power factor of the load referred to from 0 5 to 0 9, the
capacity required would be 270 microfarads, and the cost
£54 ; or to improve from 0 65 to 0 9, 190 microfarads, at
a cost of £38. It must therefore be seen that the’’
difference in capacity to improve from 0’9 to 0’95 was
very considerable, and the advantages gained might, in
most cases, not be worth the increased expense.
Replying to Mr. Watkins, who agreed with earthing
the neutral thoroughly, but suggested that the main
plant should work insulated, Mr. Jones thought this
was not to be recommended in view of the fact that all
faulty circuits should be automatically made dead,
which was provided for with eartbed neutral systems
and leakage-protective gear.

Mr. Jones was pleased to hear such an authority
as Mr. Forrest agreed with reference to earthing
the neutral, and his remarks as to the question of
periodical testing of protective gear were very much to
the point, and must be adhered to if such systems were
to be reliable. His own practice was to do this and also
to put artificial faults on periodically, in order to test
the system under working conditions as near as
possible. It was erroneous to think that, once automatic
protective gear was installed, less supervision was
required. It was certainly a great advantage to have
such devices, but the plant ought to be supervised as
thoroughly as if it were without them.

The late Mr. William Morris, of Briton Ferry, managing
director of the Baglan Bay Tinplate Company, left estate
valued at £4,337 gross.