RUBBER PLANTING 55 



the globules is only effected during the subsequent 

 pressing and working of the wet rubber. The question 

 of the extent to which polymerisation occurs during 

 coagulation appears to be still a disputed one. 



Fresh latex also contains an oxydising enzyme which 

 leads to a darkening in colour on prolonged exposure 

 to the air. The enzyme may be destroyed by im- 

 mersing the coagulated rubber for a few minutes in 

 water at 80 C. and this treatment has been recom- 

 mended as a commercial process in order to obtain 

 light coloured rubber. Such treatment can be replaced 

 to some extent by thorough washing, and completely by 

 the use of vacuum driers, in which the rubber is rapidly 

 dried at a fairly high temperature. 



