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206 PREPARATION OP INDIA-RUBBER. 
ART. LIX. — ON THE PREPARATION OF INDIA-RUBBER BY 
VULCANIZATION AND CONVERSION. 
By Mr. Brockedon. 
Mr. Brockedon's object in this communication was to de- 
scribe, —1st, a mode of treating India-rubber by which new 
properties are imparted to this substance ; 2d, the new 
uses in the arts to which these acquired properties now ren- 
der India-rubber applicable. Vulcanization and conver- 
sion denote that combination of India-rubber with sulphur 
from which the new properties about to be described result. 
The process of conversion consists in submitting India-rub- 
ber to the action of bisulphuret of carbon mixed with chlo- 
ride of sulphur. The caoutchouc cannot, however, be 
penetrated by this process to any depth ; and therefore it 
is inapplicable when the mass to be acted on is thick. The 
process of vulcanization, which seems to be more applica- 
ble, is the result of many experiments made by Mr. Han- 
cock ; who found that caoutchouc, when immersed in a 
bath of fused sulphur, heated to various temperatures, by 
absorbing the sulphur, assumed a carbonized appearance, 
and lastly acquired the consistency of horn. It was in the 
course of these changes that it attained the state of vulcani- 
zation which Mr. Brockedon afterwards described. The 
same vulcanized condition can, however, be produced either 
by kneading the India-rubber with sulphur and then ex- 
posing it to a temperature of 190°, or by dissolving the 
India-rubber in any known solvent, as turpentine, previously 
charged with sulphur. Having thus explained the processes, 
Mr. Brockedon described the effect which they produced 
on the caoutchouc: — 1st, the India-rubber, thus treated, re- 
mains elastic at all temperatures ; in its ordinary state it is 
quite rigid at a temperature of 40° ; 2d, vulcanized caout- 
