2i8 RUBBER AND 



partially vulcanised become more fully vulcanised on 

 keeping. It is therefore the practice to vulcanise the 

 majority of goods rather less completely than is finally 

 required. 



Some recent writers still regard the process of 

 vulcanisation as one of adsorption. That is to say 

 they look upon the vulcanised rubber as existing in 

 a condition of physical mixture rather than in one of 

 true chemical combination. As previously stated, the 

 whole problem is one of extreme difficulty, and we are 

 perhaps still far from a final solution. 



The physical condition of the rubber has a marked 

 influence upon the final product, and the same sample 

 of raw rubber, if differently worked before vulcanisa- 

 tion, requires to be vulcanised with a different quantity 

 of sulphur and to a different extent in order to produce 

 the same final result. After long continued kneading 

 and mastication more sulphur is required in order to 

 bring the vulcanised rubber to the same condition of 

 physical consistency. 



The process of cold vulcanisation with sulphur 

 monochloride was discovered by Parkes in 1848. The 

 action is exceedingly vigorous. Dilute solutions are 

 therefore employed, and the period of contact is short. 

 The solvent almost universally employed is carbon 

 bisulphide. 



The action of sulphur monochloride on rubber, like 

 that of sulphur, is an addition and not a substitution 

 process. This is proved by the fact that no sulphuretted 



