122 PARA RUBBER. 



This could be easily done by causing it to pass over a series of iron 

 pans of calcium chloride contained in a drying box outside." 



A writer in the " India Rubber Journal " objected to the use 

 of calcium chloride on the ground of expense and the danger of acci- 

 dental contamination with the rubber, and expressed his opinion 

 that the circulation of dry air was preferable to the use of this 

 chemical. Mr. Ridley, in reply to these objections in the "Straits 

 Bulletin, " stated that in a manufactory on a large scale the calcium 

 chloride would be in pans, well away and above the rubber, and that 

 there would, therefore, be no risk. If calcium chloride is allowed to 

 remain in contact with the rubber it destroys it, but if cleared off 

 immediately it does no harm. 



At Peradeniya a series of experiments has been made. A 

 current of dry hot air is made to pass rapidly through a specially 

 constructed chamber in which the rubber is arranged on a number 

 of wooden trays. The air is first dried by passing it through a series 

 of crates or cells containing hygroscopic chemicals. The crates 

 can be easily removed, dried, and replaced. The dry air is then 

 drawn over a fire by means of a fan, the latter being turned by 

 hand or power. By this means the rubber is dried fairly rapidly ; if 

 the temperature is maintained at about 90° F. ,the rubber is thorough- 

 ly dried in a few days if the sheets are not too thick, and softening 

 does not occur if the rubber is not dried too quickly. It is as well to 

 mention that the softening of rubber alone, when due to too rapid 

 drying, is not objected to by manufacturers, as the masticating pro- 

 cess, through which the dry rubber passes, converts the material into 

 a substance void of all toughness and elasticity; but any softening 

 of the rubber before it leaves the factory of the producer might 

 prove very serious as the sheets or biscuits would be bound to 

 adhere to one another, and probably become tacky before their 

 arrival in Europe. 



