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mixings free from substitute and carbon black, and having a high
coefficient of vulcanisation, which may be obtained by the use of
magnesia usta. Further, in order to render such mixings as
impervious as possible to moisture, additions of pitch, paraffin wax,
ceresine, or ozokerite maybe made. In' this connection it should
be noted that paraffin wax by itself is not absolutely devoid of the
property of absorbing a certain amount of water, yet when it is
mixed with rubber and sulphur and vulcanised, the product has an
exceedingly low absorptive power. Goods which are to withstand
high temperatures should contain no softening ingredients, and
where, in addition, they come in contact with steam only limited
quantities of substitute should be used.

The following series of examples of mixings illustrate the above
remarks. No claim is made that these mixings are possessed of
any general importance, as they can, of course, be modified in a
great variety of ways : —



No. 'i.— Packing-sheet.




. No. 4. — Packing-sheet.




Congo


. 1,500 gms.


Guayule


5,000 gms.


Pontianac mixture


. 2,000 ,,


Whiting .


. 5,000 „


Reclaimed rubber


. 2,000 ,,


Talite. " .


2,000 ,,


Waste rubber


. 10,000 ,,


Barytes


6,000 ,,


Substitute .


. 2,000 ,,


Litharge


. 1,000 .,


Barytes


10,000 ,,


Graphite


3,000 „


Lithopone .


15,000 „


Sulphur


500 ,.


Sulphur


300 „


Magnesia usta


200 ,






Hemp fibre .


2,500 ,,


No. 2.— Packing-sheet.








Guayule
Zinc oxide .


4,000 „
8,000


No. 5. — Packing-sheet.
Congo .


5,000 ,,


Barytes
Sulpliur


10,000 ','
750


Pi)ntianac .
Asbestos fibre


3,000 „
10,000 .,


Magnesia usta


50 \\


China clay .


10,000 ,,


Canvas waste


7,500 ,,


Talite .


5,000 .,






Barytes


10,000 ..


No. 3. — Packing -sheet.




Japan red (iron oxide)
Castor-oil .


5,000 ,,
1,000 ,,


Congo .


. 4,000 ,,


Sulphur


1,000 ,,


Reclaimed waste .


4,000 ,,






Barytes


10,000 ,,


No. 6. — Manhole-packing.




Litliopone .


10,000 ,,


Guayule


2,500 „


Sulpliur


750 „


Pontianac mixture


5,000 ,,


Magnesia usta


100 ,,


Waste .


25.000 ,,


Waste with canvas


12,000 .,


Reclaimed waste .


10,000 ,,


Euphorbia mixture


2,000 ;,


Barytes


15,000 ,;



io6



RUBBER MANUFACTURE.



No. 6. — Manhole packing—


:ont.


No. 12.— Oil-tubing— cont.




Lithopone .


15,000 gms.


Talite. . . .


5,000 gms.


Canvas waste (proofed)


25,000 „


Pitch . . . .


500 ,,


Suliihur


],000 ,,


Sulphur


800 ,,


Magnesia usta


250 „


Magnesia usta


250 ,,


No. 7. — Water-hose.








Congo.


5,000 ,,


No. IB.— Alkali-tubing.




Reclaimed waste .


3,000 ,,


jNIozambique


10.000 „


Waste.


15,000 ,,


Waste.


5,000 „


Ponti.mac mixture


2,000 ,,


Pitch .


500 ,,


Substitute .


8,000 ,,


Talite .


5,000 ,,


Lithopone .


6,000 ,,


Lithopone .


10,000 ,,


Whiting


6,000 ,,


Sulphur


1,500 „


Barytes


6.000 ,,


Magnesia usta


200 ,,


Sulphur . . .


1,500 ,,






Magnesia usta


]00 ,,






Vaseline


500 ,,


No. lA.— Hose for latrines.








Congo .


10,000 „


No. 8. — Beer-hose.




Reclaimed waste .


7,000 ,,


Mozambique


10,000 „


Lithopone .


10,000 „


Para waste .


10,000 ,,


- Barytes


5,000 ,,


Brown substitute


8,000 ,,


Talite .


15,000 ,,


China clay .


5,000 „


Sulphur


' 1,500 ,,


Lithopone ^ .


5.000 ,,


Magnesia usta


250 ,,


Barytes


5.000 ,,


Vaseline


1,000 „


Vecretable black .


1,500 ,,






Pitch .


500 ,,






Sulphur


. 1,500 ,,


No. 15. — Heating-tuhe.




Magnesia usta


200 „


Mozambique


5,000 „






Reclaimed waste .


10,000 ,,


No. ^.— Wine-tuUng.




Barytes


5,000 ,,




Lithopone .


15,000 ,,


Mozambique
Reclaimed Para waste


10,000 ,,


Sulphur


400 ,,


5,000 ,,


Magnesia usta


75 ,,


Lithopone 1 .


5,000 ,,


Pitch .


750 ,,


China clay .


5,000 „


Vaseline


. 1,000 „


Brown substitute


2,500 ,,






Sulphur


1,500 „






Magnesia usta


250 „


No. \Q.— Oil-valves.








Cametas


. 5,000 „


No. 10. — Acid-tubing.




Guayaquil .


. 5,000 „


Para .


. 5,000 ,,


Reclaimed waste .


. 6,000 ,,


Cametas


. 5,000 „


China clay .


. 4,000 ,,


Sulphur


800 ,,


Litharge


. 4,000 ,,


JMagnesia usta


100 ,,


Sulphur


1,000 ,.


Coresine


2,000 ,,


Magnesia usta


250 „


No. U.—Acid-tnbing.




No. 17. — Para valves.




Para .
Cametas


. 2,500 „
. 7,500 ,,


Para .

Cametas


. 5,000 ,,
. 5,000 ,,


Sulphur
Magnesia usta
Talite .


1,000 ,,

50 „

. 2,500 ,,


Sulphur
Magnesia usta


800 „
75 „


Barytes


. 2,500 ,,


No. 18. — Acid valves.




No. \2.— Oil-tubing.




Cametas


. 10,000 „


Guayaquil .


. 10,000 „


Ceresine


1,000 „


Reclaimed waste ,


. 5,000 „


Sulphur


. 1,500 „


Litharge


2,500 ,,


Magnesia usta


.^0 „



^ This lithopone should contain only traces of zinc compounds soluble in acetic,
tartaric, or lactic acid.



THE MIXINGS.



107



No. 19. — White (drab) valves for water.



Mozambique . •
Zinc white .
Whiting
China clay .
Light substitute .
Vaseline
Sulphur
Magnesia usta

No. 20. — Condenser valves.

Mozambique
Reclaimed yaste ,
Para waste .
Brown substitute
China clay .
Lithopone .
Talite .
Litharge
Pitch .
Sulphur
Magnesia usta

No. 21. — Gas tubing.

Cam etas
Ikelemba

Para waste mixture
Pontianac mixture
Euphorbia mixture
Zinc white .
China clay .
Lithopone .
Talite.

Reclaimed waste .
White substitute .
Brown substitute.
Castor- oil .
Vaseline
Sulphur
Magnesia usta



No. 22. — Gas tubing.

Congo .

Euphorbia mixture
Zinc white .
Whiting
White substitute
Vaseline
Sulphur
Magnesia usta



No. 23. — Gas tubing— red.

Mozambique
Brown substitute
China clay .
Lithopone .
Iron oxide .
Golden sulphide
Magnesia usta
Ceresine



10,000 gn:
5,000
6,000
6,000
8,000
1,000
1,250
200



10,000
5,000
5,000
5,000
5,000
2,500
2,500
2,500
250
1,250
250



1,000
4,000
1,500
1,500
1,000
10,000
7,500
7,500
5,000
5,000
5,000
5,000
1,000

500
1,000

150



8,000

2,000

15,000

10.000

10,000

500

1,500

250



10,000
5,000
4,000
6,000
6,000
1,500
300
250



No. 24. — Gas tubing— black.
Negroheads .
Pontianac mixture
Black substitute .
Barytes
Talite .
Litharge

Vegetable black .
Sulphur
Magnesia usta
Pitch .
Vaselin'e

No. 25. — Drainage tube.
Mozambique
Brown substitute
China clay .
Lithopone .
Golden sulphide
usta



No. 2Q.—Mats.
Niggeis

Pontianac mixture
Reclaimed waste .
Waste (ordinary) .
Talite .

Vegetable black .
China clay .
Canvas waste
ParaflBn wax
Sulphur

No. 27. — Bottle Washers.
Para .
Columbian .
Black substitute .
Golden sulphide .
usta



No. 2%.— Bottle Washers.
Cametas
Black substitute
China clay .
Golden sulphide
Magnesia usta

No. 22.— Bottle rings [Codi
Para .
Mozambique
Brown substitute
Talite .
China clay .
Magnesia usta
Golden sulphide
Paraffin wax

No. 30.— Buffers.
Para .
China clay ,
Soap - stone (Stearin

talkurn)
Litharge
Pitch .
Sulphur ,



8,000 gms.
2,000
5,000
5,000
10,000
2,000
2,000
1,000

300

500
1,500



10,000
2,000
5,000



15,000

2,500

250



5,000

2,000

15,000

20,000

15,000

1,000

5,000

5,000

2,000

800



4,000
6,000
3,000
1,000
350"



10,000

3,000

2,000

1,000

300

s rings).
5,000
5,000
3.000
3,000
1,000
75
1,500
200



000

000



1,000

1,000

250

400



io8



RUBBER MANUFACTURE.



No. 31. — Buffers for insidati





Guayule


6,000 gms.




Pontiaiiac mixture


.^,000 ,,




Eeclaimed rubber.


25,000 .,




China clay .


30,000 ,,




Litharcfe


5,000 .,




Vegetable black .


500 ,,




Sulphur


500 ,,




Magnesia usta


250 ,,




Pitch .


1,000 ,,




Vaseline


500 ..


No


32. — Ruhher stoppers (corks).




Negroheads .


10,000 ,,




Sulphur


800 ,,




Magnesia usta


150 .,


No


33. — Rubber stoppers (corks).




Neirroheads .


10,000 ,,




Taiite


3.000 .,




Sulphur


. 1,000 ,,




Magnesia usta


100 ,,




Ceresin


250 ,,


No


. 34. — Rubber stop)pers (c


orks).




Para .


10,000 „




Ceresin


. 2,000 ,,




Sulphur


1,000 ,,




Magnesia usta


100 „


No


Zb.—Cab tyre.






Para .


5,000 ,,




Congo .


. 8,000 ,,




Zinc white .


. 10,000 ,,




China clay .


. 10,000 ,,




Taiite .


5,000 ,,




Reclaimed rubber


. 5,000 ,,




Litharge


. 2,500 „




Pitch .


500 „




Sulphur


800 „


No


. 36. — Washing -machint


rollers.




Mozambique


10,000 ,,




Euphorl>ia mixture


1,000 .,




Lithopone .


. 10,000 .,




Barytes


. 5,000 ,,




Taiite .


. 5,000 ,,




White substitute .


. 5,000 ,,




Parathn wax


500 ,,




Sulphur . ■


. 1,000 ,,




Magnesia usta


350 ,,


No


. 37. — Diaphragms, for


compressed air.




Para .


. 10,000 gms.




Pitch .


100 ,.




Sulphur


. 1,000 ,,



No. 38. — Canvas hose.

Mozambique
Poiitianac mixture
Reclaimed rubber
Taiite .



150



5,000

1,.^)00

5,000

10,000



No. 38. — Canvas hose— cont.

China clay . . . 10,000 gms.

Litharge . . . 1,500 ,,

Sulphur . . . 900 ,,

Magnesia usta . . 200 ,,

No. 39. — Sponge rulber.

Congo. . . . 5,000 ,,

White substitute . . 2,500 ,,

Taiite . . . . 8,000 ,,

Whiting . . . 4,000 ,,

Ammonium carbonate . 1,500 ,,

Oil of turpentine . 600 , ,

Sulphur . . .• 400 ,,



No. AO.— Rat-box.

Para .... 5,000

Cametas . . . 5,000

Brown substitute . . 2,000

Sulphur . . . 1,000

Magnesia usta . . 75

Pitch .... 100



No. Al.— Billiard-strip.

Negroheads (pale) . 5,000

Substitute (floating) . 1,000

China clay . . . 1,000

Golden sulphide . . 500

Magnesia usta . . 50

Paraffin wax . . 100



No. 42. — Elastic bands.

Para . . . .4,000
Congo. . . . 6,000
Brown substitute (floating) 2,500
China clay . . . 2,000
Golden sulphide . . 1,500
Vermilion ... 200

Magnesia usta . . 50

No. 43.— ^a//s.



No.



Congo .


9,000 „


Brown substitute


1,000 ,,


China clay .


5,000 ,,


Zinc white .


12,000 ,,


Waste


5,000 ,,


Paraffin wax


500 .,


Sulphur


1,000 ,,


Magnesia usta


100 ,,


44. — Frictions.




Upper Congo or Ikelem


ba 8,000 ,,


Reclaimed rubber


7,000 ,,


Brown substitute


5,000 .,


Pontianac mixture


1,000 .,


Lithopone .


15,fi00 ,,


Whiting


2,000 ,,


Canvas waste, proofed


5,000 ,,


Sulphur


. 2,000 ,,


Magnesia usta


500 „





THE MIXINGS.


109


No. i5.— Asbestos solution.




No


48. — Fara sheet for cables.


Guayule


25,000 *gms.




Para la, old


20,000 gms.


Dead Borneo


1,500 „




Sheet Balata


1,500 ,,


Substitute .


7nO ,,




Sulphur


1,800 ,,


Barytes


5,000 ,,








Zinc white .


15,000 ,,


No


49. — Fara sheet for cables.


Sulphur


1,000 ,,




Para .
Ozokerite .


20,000 „
1,000 „


No. 46. — Insulating tape.






Paraffin wax
Sulphur


1,000 „
2,000 ,,


Guayule


5,000 ,,








Flakes


2,000 ,,


No


50.— Cable rubber (for 1


tube-machine).


Barytes

Vegetable black .
Lithopone .
Tar, thickened .
Castor- oil .
Mica powder


20,000 ,,
2,500 .,

10,000 .,
2,000 ,.
1,000 ,,
1,000 ,,




Para .

Congo

Balata

PontianRC mixture

French chalk

China clay .

Zinc white .


2,000 gms.
6,000 ,,
2,000 ,,
2,000 ,,
6,000 ,,
. 4,000 ,,
5,0nO .,


No. A7.— Cable rubber.






Litharge


. 2,000 ,,


Para .


3,000 ,,




Sulphur


700 „


Congo .


7,000 ,,




Magnesia usta


175 .,


Litharge


1,000 ,,




Ceresin


2,000 .,


China clay .


10,000 ,,




Vaseline


3,000 ,,


French chalk


3,000 ,,








Pitch .


700 ,,


No


61.— Thread.




Sulphur


■ 500 ,.




Para la, old, sorted


10,000 ,,


Magnesia usta


300 ,,




Sulphur


750 „



Preparation of Golden Sulphide. — Bright red rubber goods, in
the manufacture of which large quantities of golden sulphide of
antimony are used, enjoy special favour, and on account of the
importance of this pigment we may here be permitted to give an
outline of its method of preparation.

Ordinary golden sulphide is obtained by decomposing sodium
sulphantimoniate — Schlippe's salt — with an acid, for which purpose
dilute sulphuric acid is generally employed. The Schlippe's salt is
obtained by fusing together antimony ore (sulphide), dry sodium
sulphate, charcoal and sulphur, extracting the melt with water, and
concentrating the aqueous solution until the Schlippe's salt crystal-
lises out. The crystals are centrifugalised in order to free them
from mother-liquor, and then dried. An alternative method con-
sists in boiling the black native sulphide with milk of lime, sodium
carbonate, and sulphur, filtering and concentrating the filtrate to
the point of crystallisation, the crystals being treated as above.
The Schlippe's salt, obtained by either method, is then dissolved in
water and the solution poured slowly into cold dilute sulphuric acid ;
the golden sulphide which separates out is allowed to settle in
absence of air and light ; the supernatant liquid is decanted, and
the sulphide is then filtered off, washed free from acid, and dried in
the dark, away from the air. In order to prevent the liberation of
sulphuretted hydrogen, which is not only unpleasant but harmful,



no RUBBER MANUFACTURE.

the solution of Schlippe's salt may be precipitated by means of a
solution of antimonious chloride, in which case a mixture of SbgSg
and SbgSg in equimolecular proportions is obtained.

Knapp's golden sulphide, so-called, or antimony cinnabar, is
obtained by the action of a solution of antimonious chloride on a
solution of sodium thiosulphate, and forms a deep red powder.

Ordinary golden sulphide, the product first described, is anti-
monic sulphide (SbgS^^), and imparts a yellowish-red colour to
mixings in which it is employed. The mixture of sulphides next
described is antimony sulpho-sulphide, and gives a vermilion red
colour. The last described, antimony vermilion, is antimony
oxysulphide, and the colour produced by it is a cherry -red or wine-
colour.

Ordinary golden sulphide dissolves readily in cold ammonium
sulphide. Knapp's golden sulphide is only partially soluble in hot
ammonium sulphide, but dissolves completely in sodium sulphide
solution on prolonged heating. In addition to determining the
actual shade and comparing it with standard, samples of golden
sulphide should be tested to see that they are absolutely neutral,
and the percentage of free sulphur should also be determined, by
extracting the sample, in an apparatus similar to a Soxhlet's extrac-
tion apparatus, with carbon bisulphide which has been purified by
distillation over oxide of lead.^

Manufacture of Substitutes. — In what follows we propose to
give such details of the preparation of substitutes as will enable
anyone to obtain a product quite free from any objectionable
features. The data to be found in technical literature on the
preparation of substitutes are in part very antiquated recipes of
individual chemists, and in part excerpts from patent specifications,
which are certainly possessed of little value. Even respectable
journals are sometimes deceived, and we find them publishing, for
example, recipes according to which substitute can be prepared by
treating an oil with sulphuric acid. It is not often that one is able
to trace the origin of the absurdity. In the instance just cited the
wortliy "professional scribe " has confused Schwefelchlorilr (chloride
of sulphur) with Schivefelsdure (sulpliuric acid), in all probability
because in the particular factory from which the recipe came
chloride of sulphur happened to be called for the sake of brevity
Sdure (acid), a practice common to many factories.

It would be outstepping the purpose of this book to describe
every process by which a useful *' substitute " can be produced. It
^ Cf. Esdi and Balla, Chemiker Zeitimg^ 1904, xxviii. No. 50.



THE MIXINGS. Ill

must suffice to deal with the most important kinds of substitute
as examples.

We have, in the first place, to distinguish between the two classes
of substitute, (a) the " chlorosulphide " substitute, which is white,
and (6) the "sulphide" substitute, which is almost black in a
compact mass, but varies in colour from yellow to brown when
ground up. In each class of substitute a distinction is made be-
tween " fatty " and " dry," as well as betweeen " floating " and
" non-floating " qualities.

White, floating, dry substitutes are prepared from rape oil —
sometimes mixed with castor oil — and chloride of sulphur in such
proportions as will completely " saturate " the oil. According to
Henriques, pure rape oil requires for complete " saturation " the
addition of 25 per cent, of its own weight of chloride of sulphur,
whilst pure castor oil requires 20 per cent. ; poppyseed oil, 35 per
cent.; linseed oil, 30 per cent.; cottonseed oil, 45 per cent.; and
olive oil, 25 per cent. The chloride of sulphur is, however, gener-
ally diluted with benzine before adding it to the oil, or else the oil
or mixture of oils is itself dissolved in benzine. By this means a
spongy mass of white substitute is obtained. The preparation is
carried out in capacious hemispherical earthenware pans, and the
mixture is vigorously stirred, both before and after the addition of
the chloride of sulphur. If, for example, 15 kilos, of castor oil
and 10 kilos, of rape oil are to be used, the amount of chloride of
sulphur required will be 5 "5 kilos., and to this 1 kilo, of light
benzine can be added with advantage. If a slightly less dry
substitute be required the proportion of chloride of sulphur must
be diminished. The substitute so obtained is ground up and placed
on racks in a room in which it is allowed to dry off, the air in the
room being rapidly renewed. Very often shallow trays containing
quicklime are placed in these racks between the shelves on which
the substitute lies, so that the acid vapours given off are absorbed
by the lime. In other cases magnesia is dusted • over the substitute
with the same end in view, and also with the further object of
counteracting the softening effect of large additions of white
substitute to a mixing. Substitute treated in this way can, how-
ever, only be used in hot-cured goods. There are makes of sub-
stitute on the market which contain as much as 5 per cent, of
magnesia, and although these are certainly specifically heavier than
other sorts, the results obtained with them on vulcanisation are far
superior. It is also customary in some instances to wash white
substitutes, but the practice is not very frequently adopted.



112 RUBBER MANUFACTURE.

Fatty white substitutes are prepared, as already stated, by using
a lower proportion of chloride of sulphur, and sometimes by modi-
fying the proportion of rape to castor oil at the same time. Hence
there are numerous possibilities of variations in the process. One
such variation may be instanced, viz. 25 kilos, of rape oil, 4"3 kilos,
of chloride of sulphur, and 1 kilo, of light benzine.

It may be added that satisfactory results can also be obtained
by the use of other oils, but it is impossible to go into details.
Many manufacturers work out, for their own special use, a substitute
which would be ill-suited for sale in the open market, but which
is cheap and suits their own purposes, and can therefore be used in
their own manufactures without any hesitation.

In brown substitutes, also frequently known as "black," a
distinction is made between substitutes made from the raw oil and
those made from blown oils. Amongst the latter the so-called
" Para-factis," which contain mineral oils, vaseline or paraffin wax,
are deserving of special mention.

The following recipe may be quoted as an example of the pre-
paration of a very useful brown substitute : — 100 kilos, of raw
rape oil are heated at about 160° C. with 16 to 18 kilos, of sulphur
in a suitable vessel provided with tipping gear. Heat may be
applied either by means of a gas-ring burner or by steam ; in the
latter case a jacketed vessel must be used. The liquid mass is
carefully stirred whilst being heated until just before the conclusion
of the process, a point which is to be recognised by the liquid
frothing and seething up in the vessel. The stirring is done with
a paddle (generally a wooden one), and its main object is to prevent
the fused sulphur from collecting on the bottom of the vessel.
There is no object in using finely ground sulphur, because the
sulphur first melts and sinks to the bottom of the vessel, and it
therefore makes no difference whether flowers of sulphur or block
sulphur is employed. Much higher proportions of sulphur than
those given above may be used, but it should be borne in mind
that goods manufactured from such substitutes behave differently
on vulcanisation from those containing substitutes with lower
proportions of sulphur. On account of the frothing which occurs,
a very capacious vessel should be used. It is advisable, after the
last vigorous reaction is at an end, to pour out the contents of the
heating vessel into large shallow pans, where it sets to a dark mass ;
this when quite cool is finely ground. A substitute prepared in
this manner is exceedingly elastic, and mixes well with rubber.
When heated to a temperature of 145° to 155° C, and subjected to



THE MIXINGS. II 3

slight pressure, it again becomes viscous, and therefore distributes
itself very evenly throughout the mass of rubber, in the case of
goods vulcanised under high steam pressure, even if the mixing has
been imperfect. By slight modifications of this process, having as
their object the combination of larger proportions of sulphur with
the oil, substitutes of a stifFer consistency, which are, however, at
the same time harder and not so easily liquefied during vulcanisa-
tion, can be obtained ; hence many processes similar to the above
are in simultaneous use, in order to meet the needs of diflferent
consumers.

The brown substitutes prepared as described above are always
non-floating. It is often desirable, however, to use substitutes
which are specifically ver}^ light, and to meet this requirement the
oils are oxidised before being submitted to a gentle sulphuration.
The oils are heated for several days, a current of air being mean-
while passed through them, and they are then treated with sulphur.
As a rule, however, the substitutes obtained in this way do not
quite float, although some firms have succeeded in producing some
fine floating substitutes solely by this method, without any addition
of mineral oil or paraffin wax. The non-floating substitutes from
oxidised oils are generally prepared in the rubber factory itself,
whilst the really floating kinds, the so-called " Para-factis," are
often referred to special substitute factories. A variety of products ' ;

can be obtained, according to the duration of the oxidising process, , - f-,

and the amount of sulphur added. Generally speaking, it may be -
said that a substitute made from an oil that has been very fully "^

oxidised, and to which a correspondingly smaller proportion of -^

sulphur has been added, is specifically lighter, but has at the same
time a considerably higher melting-point than one which has not
been oxidised for so long a time. Some manufacturers, at least?,
prefer to use for inner tubes and similar qualities substitutes of low
melting-point rather than those which melt at a higher temperature.
The best plan would appear to be, therefore, to ascertain by experi-
ment the kind of substitute most suitable for each particular
purpose, and not to treat all brown substitutes alike.

It it be desired to prepare the so-called Para-factis in the
factory, oxidised castor oil must be used instead of oxidised rape
(according to Hohn), and to this one-third of its own weight of
vaseline, or of a mixture of mineral oil and paraffin wax. must be
added. The sulphuration is then carried out in the manner
described..

Special kinds of substitute, to which asphaltum or ordinary

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