1 68 Biffen . — The Coagulation of Latex . 
As the rubber exists in particles in the latex, it seemed 
possible that the centrifugal method of separation might be 
adopted in examining the phenomena of coagulation. 
A modified form of the ordinary centrifugal milk-tester was 
therefore designed capable of being rotated some 6,000 times 
per minute. 
The latex was taken directly from the trees, strained 
through wire-gauze to remove any pieces of bark, and then, 
if very thick, diluted to about the consistency of thin cream. 
The first experiments were made with the latex of Castilloa 
elastica. After centrifugalizing for from three to four minutes, 
the rubber- particles completely separated as a thick, creamy, 
white layer, from the deep brown solution containing tannic 
acid in which they had been suspended. This layer was 
taken off, shaken with an excess of water to thoroughly wash 
it, and again separated. The separated particles were then 
shaken with water so as to form an emulsion, and alkalies 
were added. No coagulation now occurred, even though the 
mixture was allowed to stand for several days. The particles 
could however be brought into a solid mass by pressure, by 
gently heating, or by drying off the water with a porous tile. 
So prepared, the rubber formed a pure white mass, without 
any trace of its usually characteristic smell. On exposure to 
the air for several days the surface gradually became brown, 
probably owing to oxidation. 
The percentage of rubber in the latex was estimated at the 
same time by separating 50 c. c. The weight of the dry 
substance was 12-5 grammes, which, as the specific gravity 
of Castilloa elastica latex is practically i-o, gives a yield of 
25 per cent. 
On treating the latex of Hevea brasiliensis in the same way 
for a slightly longer time a similar separation occurred. The 
same purely physical means as those employed in the case 
of the separated Castilloa rubber-particles caused them to 
coalesce to form a solid mass, while the addition of acetic 
acid and the action of the smoke of burning urucuri nuts had 
no effect. 
