169 
Biffen . — The Coagulation of Latex. 
The yield of rubber, estimated as before, was from 28 to 30 °/ o . 
The latex of Manihot Glaziovii also separated readily and 
gave results completely parallel with those mentioned above. 
This latex is interesting, as it is readily clo ted by churning. 
A soft spongy clot is formed in a few minutes containing 
in its meshes the greater part of the solution in which the 
rubber-particles were suspended. If this clot is cut into slices 
while still soft, and pressed between sugar-cane crushers, or in 
a heavy press, the bulk of the solution is extracted and a 
fairly pure rubber is found. On drying it does not give off 
the putrid smell characteristic of the ordinary Ceara ‘ scrap.’ 
Other latices can also be clotted by churning, but the 
process is a long one. 
The latex of Hancornia speciosa and of Mimusops globosa 
gave similar results on centrifugalizing. In the case of the 
latter the pink colouring-matter which characterizes ‘ balata ’ 
was found to have separated as a thin layer at the bottom of 
the tubes. 
Artocarpus incisa (Linn.) contains a very viscous latex 
employed by the Brazilians as a bird-lime or as a substitute 
for glue. When diluted and centrifugalized it separates 
readily, giving a creamy white layer which dries to a resinous 
mass somewhat resembling gutta-percha. At the ordinary 
temperature this is quite hard and brittle, but if the tempera- 
ture is raised slightly it becomes plastic, and at the temperature 
of boiling water it is soft and excessively sticky. The substance 
is soluble in carbon bi-sulphide, and insoluble in alcohol and 
water. 
Urostigma gamelleira (Miq. 1 ) yields a similar substance of 
a chocolate-brown colour. 
We thus see that the mere action of centrifugal force effects 
the separation of rubber ; and from the failure of the processes 
usually employed, involving the use of chemical reagents, to 
bring about the clotting of the separated and washed rubber- 
particles, we must infer that no chemical change occurs in the 
1 Mart. FI. Bras. 4. 1. 93, Ficus doliarum of Mart. Sys. Mat. Med. Bras. p. 88. 
N 2 
