108 



the product, and this being so, we are more easily able to apply 

 a remedy which consists in unifoi'mity of method of preparation. 

 Further the information derived from the elucidation of the cause of 

 variability has enabled us to realize the second problem, viz., the 

 preparation of an improved type of raw rubber and it is essentially 

 with this problem that I propose to deal. 



Returning once more to the cause of variability, we have found 

 that variability in rate of cure of the raw product is brought about 

 by two factors : (1) the amount of an accelerator or catalyst produced 

 in the raw rubber from the nitrogenous constituents of the latex 

 by allowing the coagulum to mature for about six days before 

 machining, and (2) the amount of some accelerating substance in the 

 latex which is retained in the rubber by some process of preparation 

 in which all the serum is retained. 



The first of these substances, which has the greatest influence, 

 especially in small quantities, we have found to be some decomposition 

 product of the nitrogenous constituents. The second substance 

 exists originally in the latex and is removed almost entirely when the 

 fresh coagulum is converted shortly after coagulation to thin ci-cpe. 



In dealing with the first of these factors, I propose only to 

 summarize the factors which will influence the amount of such 

 accelerator in the rubber. They are as follows : 



(1) Amount of moisture in the prepared rubber ; 



(2) Amount of serum retained ; 



(3) Rate of drying ; 



(4) Thickness of coagulum before and after machining ; 



(5) Presence of antiseptics, e.g., formalin, sodium sulphite 



and sodium bisulphite ; 



(6) Influence of different coagulants ; 



(7) Excess of coagulants, especially of certain coagulants ; 



(8) Influence of smoking ; 



(9) Influence of artificial methods of drying ; 



(10) Action of various chemicals on the finished rubber in 



retarding or accelerating rate of cure ; 



(11) Concentration of latex ; 



(12) Action of water as a solvent. 



.' . * 

 In dealing with the second accelerating factor the factors which 



influence the amount present are : 



(1) Concentration of latex ; 



(2) Effect of water as a solvent on the finished rubber. 



Whether other factors, such as the nature of the coagulant, 

 or an excess of coagulant, antiseptics and other chemicals or 

 smoking, have an effect on rstpidly curing rubber, the rapidity of 

 cure of which is due to some constituent of the latex normally 



