56 CAOUTCHOUC OE DTDIAEUBBHR (Pam). 
process is then washed, rolled, and dried, and finally placed on 
the market as “ biscuit ” or “ sheet ” rubber. The addition of 
certain chemical reagents to the latex, hot or cold, brings 
about coagulation; dilute mineral acids, acetic acid, and tan¬ 
nic acid are particularly active. Coagulation may also be 
hastened by exposing the latex to heat and the products of 
combustion of a fire, the latex being coagulated fractionally 
by such a process and the finished product, when properly 
manufactured, is said to be less liable to putrefaction than the 
rubber prepared by many other methods. The smoke from 
burning palm nuts (Attalea excelsa. Mart., and Maximiliana 
regia, Mart.) contains, among other substances, small quan¬ 
tities of acetic acid, acetone, and creosote. The acetic acid is 
probably the agent responsible for effecting the coagulation ; 
the other substances, particularly the creosote, are absorbed, 
the latter acting as an antiseptic. The decomposition of the 
albuminous or proteid substances in the latex may be prevent¬ 
ed by the addition of suitable antiseptic reagents to the latex 
when the rubber is prepared in other ways, though quickness 
in drying and complete extraction of the moisture from freshly- 
coagulated rubber is often sufficient to bring about the same 
result. 
Coagulation by chemical reagents is commonly adopted on 
estates. Many compounds such as picric acid would rapidly 
coagulate the proteids, but the effect on the resulting rubber 
would be bad. It has been shown that many acids may be 
used in the coagulating process, but it is unnecessary to do 
more than mention those 'which have, from practical expe¬ 
rience, been proved more or less acceptable to producers in 
the tropics and manufacturers in Europe. 
Acette acid. This is cheap, always procurable, is not dan¬ 
gerous to handle and is as effective as formic acid. It is not 
as powerful as tannic acid, though it is effective in bringing 
about the coagulation of the latex while cold. The commercial 
article varies in strength, and the quality should be noted by 
the purchaser. 
