1 66 Biffen . — The Coagulation of Latex. 
on a larger scale, in Mexico, Brazil, and the West Indian 
Islands. 
Rubber-yielding plants which always have laticiferous cells, 
were for the most part chosen on account of the ease with 
which large quantities of latex could be obtained, and because 
the various processes used in the preparation of crude rubber 
seemed likely to throw some light upon the subject. 
A microscopic examination of any one of these latices 
shows that its milky appearance is due to the presence of 
innumerable small granules of caoutchouc, which in themselves 
are soft and sticky, for they readily cohere to form a small 
mass of rubber if the cover-glass is lightly rubbed on the 
slide. 
Some of the processes employed to prepare this rubber 
may be described here. 
In the preparation of Para rubber, a thin layer of the latex 
of Hevea brasiliensis (Muell. Arg.) or other species of Hevea , 
is exposed to the action of the smoke of burning ‘ urucuri ’ 
nuts ( Attalea excelsa, Mart.); coagulation is immediately 
brought about, resulting in the formation of a soft, curdy mass 
of rubber, which on drying becomes tough and elastic. 
The same process is now being applied with good results to 
the preparation of Ceara rubber from the latex of Manihot 
Glaziovii (Muell. Arg.). 
The usually accepted explanation of this is that the water 
contained in the latex is simply evaporated off 1 ; but as the 
coagulation is brought about in so short a time, and moreover 
as there is no loss of weight on its occurrence, this is obviously 
incorrect. 
On passing the smoke of the burning Attalea nuts through 
a condenser, condensation occurs and two layers of liquid are 
found in the receiver, one colourless and limpid, the other 
dark brown and oily. If these are separated by means of 
a pipette, or with a moistened filter paper, and analyzed, the 
former is found to consist mainly of acetic acid, and the latter 
of creosote and traces of pyridine derivatives. 
1 Ernst, Trinidad Bulletin, vol. iii. p. 235. 
