LATEX. 67 



If it be desired this process can be retarded by adding 

 ammonia or formalin. Although both these reagents produce 

 the desired effect, their action on the latex is entirely different. 



The ammonia does not prevent decomposition but neutralises 

 the acids formed by the action of the bacteria, whereas formalin 

 prevents decomposition by antisepticising the albuminous matter 

 and thus preventing the growth of bacteria. 



The amount of ammonia required can be ascertained by 

 testing with litmus paper till a neutral solution is obtained. 

 Weber suggested the addition of i oz. to i oz. of formaldehyde 

 (40 per cent, solution of formalin) to every gallon of latex to keep 

 the proteids inactive. 



