19 



Shaking or churning has proved useless and the usual coagulants ' 

 have failed to produce coagulation. 



The method I have devised is as follows : — 



The latex is warmed to 40 C and a solution of tannic acid of 

 known strength is prepared, the solution I used being of 2 per cent 

 strength. This solution is added to the latex until there is one per 

 cent of tannic acid present in the latex. In the case of a two psr cent 

 solution of tannic acid this will naturally mean the addition of the 

 solution in the proportion of one to 19. The mixture is then gently 

 beaten or churned. Violent agitation leading to the formation of 

 froth should be avoided while simple shaking or stirring is not very 

 efficient. 



In one or two minutes the whole mass sets to a cream which on 

 gentle agitation becomes quite coherent and which then may be 

 lifted out by hand, rolled or washed on a washing machine. The 

 coagulation is complete, the liquid remaining being clean or at most 

 faintly opalescent. 



This method is quite successful with natural latex, but if the latex 

 be diluted with water the process is more difficult to carry out and 

 more of the tannic acid solution is necessary. 



Tannic acid is not corrosive. It is bought in the solid state and the 

 price in London is 2/- a pound. One pound of acid will be sufficient 

 for preparation of 300 to 400 pounds of dry rubber. 



This process as described I believe to be quite new and it is essen- 

 tially a practical process for use on rubber estates. 



P. J. BURGESS, 

 Government Analyst Labor at ar v. 



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