Biffen . — The Coagulation of Latex. 171 
up particles in suspension when clotted for the purpose of 
clearing jellies. We may even push the old analogy of blood 
and latex further, and compare the formation of a rubber-clot, 
in many cases, to the formation of a blood- clot, the rubber- 
particles being bound together by coagulated proteids in the 
same way as the blood-corpuscles are bound together by fibrin. 
In this case, however, we must remember that the rubber- 
particles, owing to their being sticky bodies unprotected by 
any external film, as e.g. the fat-particles of milk are, are 
capable of aggregating together of their own accord to form 
a solid mass. 
Rubber then, as now prepared, contains among other 
substances proteid matters. To these must be ascribed the 
well-known * fermentative change ’ which causes a considerable 
loss by converting the solid blocks of rubber into a foul- 
smelling spongy substance. In the Para rubber the creosote, 
absorbed from the smoke of the burning nuts, acts as an 
antiseptic and prevents this proteid decomposition k 
To test for the coagulated proteids is not an easy matter; 
continued boiling with a concentrated solution of caustic 
potash will however extract small quantities of alkali- 
albumin. £ Balata ’ gives good results most readily. On 
extraction with caustic potash a flocculent precipitate is 
obtained, which is readily soluble in dilute nitric acid, and is 
reprecipitated on the addition of alkalies. Boiling precipitates 
it either in acid or alkaline solutions, and it gives no precipi- 
tate with acetic acid and potassium ferro- cyanide. The 
proteid is thus identical with the albumose described by 
Green from the latex of Mimtisops globosa. 
1 Cf. the smoking of fish &c. for preserving purposes. 
Botanical Laboratory. Cambridge, 
February , 1898. 
