ArcusT 1, 1898.] THE TROPICAL AQRICULTURIST, 
85 
ARTIFICIAL INDIA RUBBER. 
WHAT NEXT ? 
One of the most recent important events in the 
history of chemistry was the discovery by an English 
professor tliat a substance corresponding in every 
respect to India rubber may be produced from oil of 
turpentine. Dr. W. A. Tilden, Professor of Chemistry 
in Mason College, Birmingham, began a series of ex- 
periments with a liquid hydro-carbon substance, 
known to chemists as isoprene, which was primarily 
discovered and named by Greville Williams, a well 
known English chemist, some years ago, as a product 
of the destructive distillation of India rubber. In 188-1, 
siys the Keio Yorlc Sun, Dr. Tilden discovered that an 
identical substance was among the more volatile com- 
pounds obtained by the action of moderate heat unon 
oil of tuiperrtine and other vegetable oils, such as 
rape-seed oil, linseed oil and castor oil. 
Isoprene is a very volatile liquid, boiling at a tempe- 
r.iture of about 30 degrees Fahrenheit. Chemical 
analysis shows it to be composed of carbon and hydro- 
gen in the proportions of five to eight. In the course 
of hia experiments Dr. Tilden fo.md that when isoprene 
ia brought into c ntact with strong acids, such as 
aqueous hydrochloric acid f"r example, it is converted 
into a tough elastic solid, which is, to all appearances, 
true India rubber. Specimens of isoprene were made 
from several vegetable oils in the course of Dr. Tilden's 
work on those compounds. He preserved several of 
them and stowed the bottles containing them away 
upon an unused shelf in his laboratory. After some 
months had elapsed he was surprised at finding the 
contents of the bottles containing the substance derived 
from the terpentinee entirely chang.ed in appearance. 
In place of a limpid, colourless liquid, the bottles con- 
tained a dense syrup, in which were floating several large 
masses of a solid yellowish colour ; upon examination 
this turned out to bo India rubber. This is the first 
instance on record of the spontaneous change of 
ISOPRENE INTO INDIA RUBBER. 
According to the Doctor's hypothesis, this spon- 
taneous change can only be accounted for by 
supposing that a small quantity of acetij or 
formic acid had been produced by the oxidiz- 
iug action of the air, and that the presence of this 
cjmpound had been the means of transforming the 
rest. Upon inserting the ordinary chemical test 
paper, the liquid was found to be slightly acid, ft 
yielded a small portion of unchanged isoprene. The 
aitificial India rubber found floating iu the liquid, 
upon analysis showed all the constituents of natural 
rubber. Like the latter; it consisted of two substances, 
one of which was more soluable in benzine or in 
carbon bisulphiue than the other. A solution of the 
artificial rubber in benzine left, on evaporation, a 
residue which agreed in all characteristics with the 
residuum of the best Para rubber similarly dissolved 
and evaporated The artificial rubber was found to 
unite with natural rubber in the same way as two 
pieces of ordinary pure rubber, forming a tough, 
elastic compound. Although the discovery is very 
interesting from a chemical point of view, it has not 
as yet any commercial importance. It is from such 
beginnings as these, however, that cheap chemical 
substitutes -for many natural products have been 
developed. Few persons outside of those directly 
connected with 
RUBBER INDUSTRIES 
realized the vast quantities imported yearly into this 
countiy. Laet year there were brongiit into United 
States ports, bs shown by the reports of the customs offi- 
cers, no less than 34,348,U00 pounds of India rubber. 
The industry has been steadily progressive since 
the invention of macliinery for maimfacturing it 
in'o the various urticlcs of eveiyday use. The 
wondeiful growth of the India rubber inteicbts in this 
country will be seen from the statistics compiled in 
the tenth census. In 1870 there were imported 
5,122(100 pounds at an avera»p rate of §1 per pound 
in 1880 the imports were 17,83.">.(;0() pounds at an 
average price of 85 cents per pound, in 1890 lii .;) 19,000 
pounds were iuiporied at an average price of 75 cents 
per pound. The present price of India rubber varies 
ftom 75 cents per pound fcr fine Para rubber to 45 
Cints per pound for the cheapest grade. It will be 
seen that, notwithstanding the increase in importa- 
tions, the price of the raw mateiial remains at a 
comparatively high figure. Many experiments have 
been made to find a substance possessing the same 
properties as India rubber, but which could be pro- 
duced at a cheaper rate. Many of the compositions 
which have been invented have been well adapted for 
use for certain puiposes, and have been used to 
adulterate the pure rubber, but no sxibstance has been 
produced which could even appioach India rubber in 
several of its important characteristics. There has 
never been a substance yet recommended as a sub- 
stitute fcr rubber which possessed the extraordinary 
elasticity which miikes it indispensable iu the manu- 
facture of so many articles of common use. Great 
hopes were at one time placed in a product prepared 
from linseed oil. It was found that a material could 
be produce 1 from it which woulJ, to a certain 
extent, equal India rubber compositions in elasticity 
and toughness. It was argued that linseed oil varnish, 
when correctly prepared, should be clear and dry in 
a few hours into a transparent, glossy mass of great 
tenacity. By changing the mode of preparing linseed 
oil varnish, in so far as to boil the oil until it became a 
ve-y thick fluid and spun threads, when it was taken 
from the boiler, a mass was obtained v/hich, in drying, 
assumed a character resembling that of glue. Resin 
was added to the mass while hot, in a quantity depend- 
ing upon the product designed to be made, and requir- 
ing a greater or leas degree of elasticity. Many 
other recipes have been advocated at different times 
to make a product resembling caoutchouc out of 
linseed oil in combination with other substances, but 
all have failed to give iatisf action, save as an adulte- 
rant to pure rubber. 
Amo- g the best compounds in use in 
liUBBER F.4CT0EIES 
at present is one made by boiling linseed oil to 
the consistency of thick glue. Unbleached shellac 
and a small quantity of lampblack is then stirred inj 
The mass is boiled and stirred until thoroughly 
mixed. It is then placed in flat vessels exposed to the 
air to congeal. When still warm the blocks formed in 
the flat vessels are passed between rollers to mix it as 
closely as possible. This compound was asserted by 
its inventor to be a perfect substitute for caoutchouc, 
It was also stated that it; could be vulcanized. This 
was found to be an error, however. The compound, 
tipon the addition of fiom 15 to 25 percent ofpuie 
rubber, may be vulcanized and used as a substitute for 
vulcanized rubber. Compounds of coal tar, asphalt, &c, 
with caoutchouc have been frequently tested, but they 
can only be used for very inferior goods. 
The needs for a 
SUBSTITUTE lOU GUTTA PERCHA 
is even more acute than for artificial India uibber. A 
compound used in its stead for many purposes is known 
as French gutta percha. This jjossesses nearly all the 
properties of gutta percha. It may be frequently ustd 
for the same purposes and has the advantage of n. t 
cracking when exposed to the air. Its inventoig 
claimed that it was a perfect substitute for India rubber 
and gutta percha, fully as elastic and tough, and 
not suscejitible to injury from great pressure or bighJ 
tsmperature. The compo.sition of this ambitious sub« 
stance is as follows: — One part, by weight, by equal 
parts of wood tar oil and coal tar oil, or of the lat:cr 
alone is heated for several hours at a temperatu:e 
of from 252 to 270 degrees Fiihrenheit, with two 
parts, by weight, of hemp oil, until, the mass can I e 
drawn into thread. Then one-half pai t, by we'ght of 
Imseed oil, thickened by boiling, is ndded. To eac h 
100 parts of the compou:id, one-twentieth to oni • 
tenth x^rrt of ozokerite and the same qnauti y 
of spermaceti are ndded. The entire mixture is thi n 
again heated to 252 degrees Fahreniitic and onc« 
fifteenth to one-twelfth p irt of sulphur is added i 
Th" substance thus obtained, upon cooling is worked 
up in a similir manner to natural India lubber. It 
has not been successfully used, however, without tlie 
