PARA-RUBBER CULTIVATION 595 



since, but in the writer's opinion the adverse criticisms are 

 due to the confusing of distinct phenomena ; l in fact, the 

 experiments brought forward in refutation of the theory, in 

 reality, amplify it. 



The explanation he propounded is as follows. When the 

 protein dissolved in the latex comes out of solution it forms 

 a delicate network throughout the latex, entangling the 

 caoutchouc globules in the meshes. This network shrinks 

 upon itself, forming a spongy clot, which can be removed 

 from the mother liquid and compressed into a solid mass of 

 rubber. 



Latices behave differently as regards the means to be 

 employed to bring about coagulation. Manihot latex is easily 

 clotted by boiling ; not so that of Hevea. A trace of acid, how- 

 ever, coagulates the latter. In the first case Biffen considered 

 the protein to belong to the globulin class and in the second 

 instance to the albumins. He applied his theory to the 

 explanation of the means employed in the Amazon region of 

 preparing Para rubber by smoking and gave strong reasons for 

 believing that this excellent empirical native method is due to 

 coagulation. The smoke arising from the smouldering fire made 

 of palm-nuts contains both acetic acid and creosote. The 

 former coagulates the latex as it is passed over the rotating 

 wooden paddle held in the smoke ; the latter impregnates the 

 rubber as it is formed layer upon layer, thus preventing any 

 subsequent moulding or putrefaction. The wet system of 

 coagulation, now in use on the Hevea estates of the Eastern 

 Tropics, was largely suggested by Biffen's explanation of the 

 Amazon smoking method. 



My attention was early directed, in the Ceylon experiments 

 of 1898-9, 2 to this question of coagulation as it affects Hevea 

 latex. Several acids and some salts were tried, with the result 

 that acetic acid was recommended as the best reagent to be 

 used on the estates to bring about coagulation, and so for 

 the preparation of the rubber from the latex. This acid is now 

 generally employed. 



The following table gives the weight required of the 

 different reagents to coagulate completely 100 cubic centimetres 



1 Coagulation and coalescence. The latter term can be used for the fusing 

 together of the rubber globules through drying or by means of pressure. 

 3 Parkin, Circular R.B.G., Ceylon, 1899, Series 1, Nos. 12, 13, 14, 148. 



