India Rubber and Gutta Percha. 77 
This usually contains much foreign matter, some of 
which is often put in by unscrupulous collectors to in- 
crease the weight at the cost of value. In other places, 
by the application of alum to coagulate the juice, smoke 
is dispensed with. 
The first act in the process of manufacture is the 
removal of the foreign material accumulated, which is 
accomplished by boiling in water for some hours, and 
by mastication and washing by machinery. In this 
process a large loss in weight occurs, the amount 
depending on the way in which the juice was collected 
and the quantity of foreign matter inwrought. The 
reduction in the best Para is about fifteen per cent ; in 
negro-head twenty-five ; other kinds ranging up to as 
high as forty per cent. The cleaning having been done, 
vulcanisation is attained by immersing the purified mate- 
rial in a bath of melted sulphur, at a temperature of 120 
deg. centrigrade, till it has absorbed ten to fifteen per 
cent of sulphur. If permitted to remain in, it would 
probably absorb much more, but not with advantage to 
its general industrial application. At this stage the sul- 
phur is simply absorbed, and no chemical modification 
has taken place. To effect the chemical union, it is sub- 
jected to further heat, which is performed in a bath of 
glycerine raised to a temperature of 140 deg. centrigrade 
This might be accomplished in the sulphur-bath by in- 
creasing its heat, but that, as just mentioned, an excess 
of sulphur would be absorbed. The result would be 
over-vulcanisation and production of a substance resemb- 
ling that which is occasionally made and used under the 
name of ebonite. There is another process of vulcanisa- 
