CAOUTCHOTto or iNDiARUBBER (Para). 55 
carried on throughout most months of the year. The fre¬ 
quency of tapping varies, some trees being tapped every day, 
others only during alternate months and others only during 
certain seasons. 
The yield shows a considerable variation, according to the 
extent of the tapping area per tree, and the methods employed. 
Individual trees have given from 2 to 25 lb. of dry rubber per 
tree in twelve months, but large acreages have yielded quan¬ 
tities varying from § lb. to 5f lb. of dry rubber per tree, per 
year, for one or more years. 
The latex is white or pale yellow in colour, and is slightly 
alkaline or neutral when it issues from the tree. Mechanical 
impurities, such as pieces of bark, sand, &c., are usually pre¬ 
sent, but can be removed by straining. The latex shows a 
great variation in its composition, particularly in the percent¬ 
age of water ; it is usually estimated to possess from 52 to 56% 
of water, 32 to 41% of caoutchouc, 1 to 3% of proteids or 
albuminoids, and varying quantities of resins, sugars, salts, &c. 
It readily mixes with water or any alkaline solutions such as 
ammonia, ammonium sulphide, &c., and is not coagulated by 
freezing or boiling, though acids readily bring about this 
Coagulation .—The pure rubber is obtained from the latex 
by processes of straining, coagulating, washing, rolling, and 
drying. Coagulation is possible owing to the presence of the 
proteid matters in the latex ; these remain in solution so long 
as the mixture is neutral or alkaline, but are precipitated when 
the solution becomes acid. If latex is allowed to stand for 
some time, the proteid matter decomposes and acidity suffi¬ 
cient to lead to coagulation is developed, but this may be de¬ 
layed by the use of formalin or ammonia. The coagulated 
proteid is considered to act as a clarifier and to carry with 
it the suspended globules of caoutchouc and other bodies. On 
estates where the daily quantity of latex is small, it is usually 
put into shallow pans and allowed to set with or without the 
addition of acid. The cake of rubber obtained by such a 
