54 RUBBER AND 



TABLE VI 

 Composition of Hevea Latex:. 



Water 50 60 per cent 



Caoutchouc 30 45 

 Resins i 2 



Proteids 23 

 Sugar -5 



Ash -25 



The latex from old trees usually contains a con- 

 siderably larger proportion of rubber than that obtained 

 from young trees. The composition of the latex is not 

 much altered by moderate tapping, but if tapping is 

 excessive the amount of rubber present may be greatly 

 reduced. 



Coagulation. 



Freshly drawn latex is alkaline in reaction. The 

 addition of a suitable amount of any kind of acid leads 

 to coagulation and to the separation of the rubber, with 

 most of the resins and proteids, from the watery and 

 soluble constituents of the latex. 



According to the older view of coagulation, this was 

 supposed to be due to the bursting of the skins sur- 

 rounding the globules, followed by the coalescence of the 

 latter. Recent observations have shown that the globules 

 may persist in the coagulated latex. This fact seems to 

 support the view that the coagulation of Hevea latex 

 by acid consists in the formation of a network of coagu- 

 lated proteid, which entangles the rubber globules in its 

 meshes and contracts upon itself. The coalescence of 



