RUBBER 653 



During the last three years the number of chemists 

 engaged in research work in connection with the rubber 

 industry in Malaya has increased from one to nine, apart 

 from those employed for special work in England, 

 working more or less in conjunction with the former. 

 Similar if not such pronounced increases in the number 

 of research chemists have taken place in Ceylon. 



The investigations already carried out, although many 

 of them are of a preliminary nature, have proved very 

 valuable to the industry and to particular estates. 



The problem is a very interesting one, and somewhat 

 different from the usual investigations, in which chemical 

 purity of the product prepared is the most essential point. 

 We have realized for some time that percentage of pure 

 caoutchouc in commercial raw rubber is not by any 

 means the principal object at which to aim. Thus, we 

 may have two samples of raw rubber, e.g., smoked sheet 

 and pale crepe, in which the actual percentage of caout- 

 chouc is higher in the latter owing to the larger amount 

 of washing and maceration it has undergone, whereas 

 the quality of the former after vulcanization may, and 

 should, be considerably superior to the latter. Investi- 

 gation is still required as to the reason of this superiority, 

 and this is probably to be found in a study of the protein 

 content and the physical nature of the coagulum, and is 

 known to be dependent on the method of coagulation of 

 the latex and the subsequent treatment of the raw rubber. 

 It appears also, in the light of recent experiments, that 

 the rate of cure, and thus the " coefficient of vulcaniza- 

 tion " (i.e., the proportion of combined sulphur to raw 

 rubber in the cured material) is an important factor in 

 the vulcanization of various grades of plantation rubbers 

 and in rubber from different species of trees, and that 

 this coefficient of vulcanization or percentage of com- 

 bined sulphur depends, cazteris paribus 1 , on the nature of 

 the raw rubber. The variability in the plantation product 

 necessitates different rates of cure for different samples 

 in order to obtain the optimum result. If plantation 

 rubber were prepared from all estates in one or two 

 uniform grades, the manufacturer would be able to 

 purchase various shipments which would always behave 



