894

THE COLLIERY GUARDIAN.

May 3, 1918.

may be turned up in a lathe, and should then be
as good as new again. By this means a 3 in. cast
iron cock will last from nine months to a year.

High silicon metal does not withstand the action
of caustic soda, regulus metal cocks are too soft, and
those of various gun-metal or phosphor-bronze
mixtures have too short a life in proportion to the
extra cost. Arrangement should be made for deliver-
ing the water supply required for washing into the
washer in the form of a fine spray, so that agitation
by means of the screw or cone is avoided.

The charge of material to be washed is allowed to
stand, either in its storage tank or in the mixer, for
several hours, and all water is carefully drained away
before adding the first acid.

The first washing is usually a preliminary wash
of from 5 to 10 gals, of D.O.V., according to whether
the size of the charge is 1,000 or 2,000 gals. The
object of this preliminary wash is to dry the benzol
thoroughly, but it also serves to remove pyridine
bases, and to some extent attacks the more easily
decomposed unsaturated hydrocarbons.

Half an hour’s brisk agitation of‘this first wash
of sulphuric acid is ample, after which a period of
one hour is allowed for settling, and the acid is
then run off as completely as possible.

A further quantity of acid, equivalent to 2| to 3
per cent, by weight of the charge, is now run into the
washer, agitation is maintained for at least an hour,
and during the period allowed for settling a sample is
taken and tested as follows:—About 200 c.c. are
carefully filtered through glass wool into a separating
funnel and about 1 litre of water is poured through
the benzol, avoiding heavy agitation. Separate the
water, give a light wash of about 50 c.c. of 20 per
cent, caustic soda, separate the soda, wash gently
once more with water, and then filter slowly from the
separating funnel, through calcium chloride or calcium
sulphate, into a 250 c.c. retort. Distil off into a
clean receiver up to 125 degs. Cent. Mix the distillate
and filter, through calcium sulphate, sufficient for
testing with concentrated sulphuric acid. Five c.c.
of the dry distillate are then shaken with 5 c.c. of
concentrated sulphuric acid in a test cylinder for
two minutes, and allowed to settle. With pure benzol
the acid will be only very slightly coloured, but with
standard benzol the colour should not be deeper than
that of a decinormal solution of bichromate of potash.

The quantity of acid required for the first or main
acid wash largely depends on the care taken in, and
the efficiency of, the once-distilling operation. Where
washing the once-run benzol in bulk is the practice, it
will generally be found that a further additional
wash of about 2 per cent, of acid is required to produce
a cleanly rectified benzol.

During the washing with acid, the temperature of
the benzol rises to about 40 degs. Cent., and in some
cases as high as 55 degs. Cent. Excessive rise in
the temperature is chiefly due to the exothermic
reaction of sulphuric acid on the impurities present.
The reaction with unsaturated hydrocarbons is par-
ticularly violent, hence the necessity for removing
these as far as possible, before attempting the chemical
Washing. This rise in temperature is no doubt
responsible in many cases for the sulphonation of ben-
zene and xylene. In the latter case metaxylene is
very readily sulphonated, with an increase in the
evolution of heat and the production of thick acid tar.

It might be advantageous in many cases where
difficulty arises in the washing process, especially in
washing xylol mixtures, to have suitable cooling coils
fitted inside the washer.

After settling for 1-1| hours, the thick acid is run
off. As before, a sample should be tested during the
settling period. It is generally advisable to agitate
the benzol for a further 15 'minutes after the last
acid has been removed, and to settle again for about
two hours, this serving to remove a small quantity
of acid tar remaining in the cone or screw, and stick-
ing to the sides of the washer. After all the acid
tar has been removed, the benzol is treated with clean
water, allowed to fall through the benzol in the form
of a fine rain, and gently wash the sides of the washer.
Agitation with water is both inadvisable and
unnecessary.

The water is allowed 15 minutes to settle, and is
then carefully drawn off. This water washing is
repeated four or five times, and removes a quantity
of hydrocarbon sulphonates, and sulphurous acid, as
well as the sulphuric acid and tars still remaining.
After the last water washing, about 10 gals, of 10
per cent, caustic soda are added, agitated for half an
hour and allowed to settle for one hour before being
drawn off. Two further washings with water are
then necessary to finish this stage of the operations.

Yield of Rectified Prodfcts from Crude Benzol.

Crude benzols, average strength.	Once-run benzol produced.	Acid used by weight.	Total loss.	!	1  Loss on ' 95 p.c. ' washing, benzol.		85 p.c. toluol.	Solvent naphtha.	Creosote | and i residue.	Naphtha- lene salts.
	Per cent.	Per cent	1“  Per cent.	Per cent. Per cent		Per cent.	Per cent.	Per cent.	Per cent.
45 per cent, at 120 degs. C.	75	4	8	7	32	16	13	21	10
60	„	„ 120	84	6	11	9	i 45	16	8	14	6
62	„	,. 120	„	85	3	7	6	1	45	17	8	16	7
65	„	„ 120	87	7	10	8	55	6	8	17	4

It is an advantage to be able to store the washed
benzol for several days before fractionating it, to
enable as much water as possible to be separated and
drawn off before charging into the rectifying still.
The above washing process refers chiefly to washing
in bulk, but slight modifications in the amount of
acid used and the number of acid washings are the
only variations necessary for washing the separate
fractions or suitable mixtures.

Final Rectification.

The still should be worked on the same lines as
previously described for the fractionation of the once-
run products. If only standard benzol is being made,
no forerunnings are taken away, and the collection

of the benzol fraction is continued until the mixture
in the receiver tests 96 per cent, to 100 per cent, at
90 degs. Cent. This will depend on how good the
toluol fraction can be made with the plant and con-
ditions available.

In the manufacture of pure benzene, toluene, and
xylenes, the first rectified products are rewashed with
chemicals, and special precautions are taken to remove
thiophenes and alien hydrocarbons.

Thiophene is removed in a variety of ways. The
general method is to continue the washing with
sulphuric acid until a test of the washed rectified
benzene gives no reaction with isatin. The benzene
requires several treatments with acid, and the time
contact is an important factor in the operation.
Agitation proceeds for several hours before tests show
the benzene to be free from thiophene, and as the
acid to a small extent attacks the benzene, the loss
during this operation may frequently rise to 5 per
cent.

Formaldehyde and dilute sulphuric acid may be used
to convert the thiophene into condensation products
which remain behind in the still in the subsequent
fractionation, and this is one of several variations of
the methods used in Continental dye works for the
removal of this impurity.

Quite a simple method for the same purpose is to
treat the benzene with just sufficient chlorine to com-
bine with the thiophene in the cold. Chlorine is
selective in its reaction, and has a much greater
affinity for thiophene than for benzene, with the
result that chloro compounds of thiophene (in the case
of benzene) and thiotolene (in the case of toluene)
are formed. These compounds have much higher boil-
ing points than benzene and toluene, and simple
distillation is then necessary to separate them. In
tests made last year of this process after the use of
to 2| per cent, of chlorine, the benzene gave no
reaction with isatin, although it previously contained
1 per cent, thiophene.

Two rectifications, preceded in each case by efficient
sulphuric acid treatment, will generally furnish a
"pure” benzene of the standard required by dye
makers and explosives manufacturers. In the case
of toluene it is rather more difficult to produce the
pure article. For one reason, both paraffins and
unsaturated hydrocarbons are present, which have
boiling points too near to that of toluene to permit of
much purification by fractionation.

The washed rectified toluol should be collected over
a range of 105 to 120 degs. Cent. It is-then washed
with Nordhausen sulphuric acid, or with D.O.V. of
1’84 sp. gr., having an addition of 1 per cent, nitric
acid. After drawing off the acid the toluol is washed
with caustic soda solution, followed by clean water.
Washed toluol has a tendency to emulsify with water,
so that care must be taken to prevent violent agitation
in adding the final water washings.

The washed toluol is then fractionated, that portion
which boils above the limits of 108 to 114 degs. Cent,
being collected. This material will still contain
benzene, xylene, and paraffins which are not nitrifi-
able. Without additional washing a further careful
fractionation on a good column will yield 80 per cent,
pure toluene from this twice-washed and rectified
toluol.

It may be useful to those making pure benzene and
toluene to mention a reliable method for the workmen
to check the fractionation. Two thermometers should
be selected for the range of the benzene fraction, and
two for the toluene fraction. A sample of pure
benzene Or pure toluene should be distilled in parallel
during each test, at the same time as the .test sample
is being examined. In this way all outside influences
and corrections for the workmen are avoided.

Spent acid is a great nuisance, but, by boiling it
up thoroughly with steam, a thick acid tar may be
readily taken from the top. This sets quite hard when
cold, and is easily disposed of, whilst from 20 per cent,
to 35 per cent, of the acid used may be recovered.
Filtered through coke, this dilute acid is quite fit
for use in making sulphate, and a simple arrangement
for recovering and using it has been in successful
operation at the Middleton Colliery for several years.

The total loss on washing and rectification is as
follows:—Loss on distillation, from | per cent, to 2|
per cent; loss on acid washing, from 4 per cent, to
16 per cent.; loss on water washing, from 1 per cent,
to 3 per cent.

Heavier losses are noted after the water washing,
when the temperature due to the acid reactions has
been unusually high.

It would be an advantage, in returning the yields
both of crude benzols recovered and rectified products
produced, if more uniform methods pf calculating these

figures were employed. Also, for comparative pur-
poses, a change in the basis of such returns might
reveal many points relating to certain types of
apparatus, which, owing to different working condi-
tions, are at present rather obscure. As a suggestion,
results might be stated in pounds of “ pure ” benzene
and toluene per hundred pounds of volatile matter.
On such a basis it would be almost possible to compare
the yields of benzene and toluene from coals widely
differing in analysis.

The above are actual results selected for periods of
one month, during which time the quality of the
crude benzol did not vary much, and the qualities of
the rectified products made during each period were
practically the same.

APPROVED SAFETY LAMPS.

In pursuance of section 33 of the Coal Mines 4-ct,
1911, the Home Secretary has made an Order approving
certain types of safety lamps until further Order, for use
in all mines to which the Act applies, subject in each
case to the conditions specified in the schedule. The
schedules to previous Orders made under section 33 of
the Act shall take effect subject to the amendments set
forth in Part IV.

The Order may be cited as “ The Safety Lamps Order
of the 9th March, 1918.”

Part I.—Flame Safety Lamps Approved for General
Use.

Messrs. Patterson’s Type A 5 Lamp.

This spirit lamp, the general design of which is shown
in fig. 1, is a modification of Messrs. Patterson and
Company’s Type A1 Lamp,* and differs from it only in
the following respects :—

The Bonnet Ring is provided with 28 vertical air-inlet
holes of a total area not greater than 1'4 sq. in.

A Spirit Vessel with a flat or round burner, T5g- to f in.
is provided, with or without an electric igniter, instead
of the oil vessel of Type Al. The flame is adjusted by
screwing or unscrewing the spirit vessel within safe
limits allowed by the lock, which may be either magnetic
or lead-rivet. A sleeve through which the lamp-tube
passes causes the flame to be extinguished when the
lamp is unscrewed. The rotating sleeve may be fixed,
in which case the lamp can only be lighted electrically;
or removable, in which case the lamp can be lighted in
the ordinary manner.

The strength of material and attachments through-
out the lamp must be not less than in the samples sub-
mitted for the official tests on October 16, 1917. The
spirit used in each lamp must be such that the lamp shall
be capable of maintaining a light of candle power not
less than 0*30, as determined by a pentane standard, all
round in a horizontal plane throughout a period of ,
not less than 10 hours. The lamps must have been
made at the works of Messrs. Patterson and Company,
at Trafalgar - street, Newcastle-on-Tyne, and each
lamp must be marked with its name and the name of
the maker.

ELEV.-

OUTSIDE
ELEVATION

kJ.

OUTS DE I

..EVATION;

i

Fig. 1.

Marsaut Lamp,
Type A 5.

ELEVATION (PART SECTIONAL)
SHEWING OILVESSEL LOCK RING AC

Fig. 2.

Patterson Lamp,
Type E 1.

Patterson’s Type E 1 Lamp.

The lamp (fig. 2), consists of the following essential
parts:—

(1)	Bonnet or Shield of steel, iron or brass, furnished
with outlet holes immediately below the crown: provided
that the lower edges of the holes shall not be less than
t3k in. above the top of the gauze. Fitted or not
with a baffle ring near the middle.

(2)	Pillar Ring of brass, steel, or iron, liveted
to the bonnet. Provide d with 16 vertical air-inlet holes
of total area not greater than 1*00 sq. in., and fitted with
a deflector ring. Four vertical tubes, of total cross
section not more than 0’45 sq. in., enter the pillar ring
and communicate with the interior of the bonnet above
the deflector ring.

(3)	Pillars, of steel or iron, four, so arranged that a
straight line touching the exterior part of consecutive
pillars does not touch the glass.

(4)	Bottom or Lock Ring of brass, steel or iron, pro-
vided with ratchet teeth to engage the bolt of a
magnetic lock, furnished also with a downward flange
to prevent tampering with the lock. The vertical tubes
from the pillar ring communicate with the lock ring,
outside the glass, the air being distributed from a circular
recess within the lock ring, which is screw-threaded above
and below the recess, through holes in the wall of the oil
vessel, which is screw-threaded above and below the holes;
or the air may be distributed through holes in the wall of
the lock ring below the screw-thread and through cor-
responding holes through the wall of the oil vessel
"below the screw thread.

(5)	Uauze.—One, of not less than 28 S.W.G. steel
wire, 784 meshes to the square inch, with a secure flame-
tight double-lap seam, fitted to the vertical flanges of
the gauze rings and so secured to the same by punch
indentations or by rivets as to make a strong and
flame-tight joint; the gauze rings being so shaped as to
form the centralised seating for the packed flanged
rings of a Mueseler chimney, these latter rings forming
the seating for the glass.

* Safety Lamps Order of August 26, 1913.