The Action of Metals, &c., on India-rubber, 277 



a temperature of 1 50° Fah. the pure rubber and the rubber 

 composition on the cloth from which the oily and greasy 

 matters and copper were removed remained quite sound> 

 whilst the proofed cloth, in its original condition, and in 

 that from which the oily and greasy matters had been 

 removed (leaving the copper), both the rubber and rubber 

 composition had become quite hard. 



The following gives the proportion of oily and greasy 

 matters, and of copper contained in the unproofed cloth : — • 



Per cent. 

 Oily and Copper Oxide 

 Greasy Matters. (CuO). 



Unproofed black, brown, and) .^« . ^ 



white check cloth j . . • o 7 



We think no stronger proof is necessary to shew the 

 enormous influence which a very small quantity of copper 

 contained in cloth has upon india-rubber or rubber com- 

 position with which it may be covered or proofed. 



We were under the impression that the action of copper 

 on rubber had never been noticed by practical men 

 employing rubber which requires sometimes to come into 

 contact with copper. Speaking, however, to an electrical 

 engineer and copper wire manufacturer who covers his 

 wires with india-rubber, he informed one of us that the 

 injurious action of copper on rubber was well recognised in 

 his trade, and that to prevent this injurious action it was 

 necessary to have the copper wire tinned, which was always 

 done. We mentioned the matter to other electrical 

 engineers, and found that all were quite cognisant of the 

 injurious effects of copper wire on india-rubber. We found 

 that copper filings also exert a highly injurious influence on 

 thin sheets of gutta percha when placed together in a warm 

 place. 



In looking at the effects of various chemical substances 

 on india-rubber, it will be observed that the oxides of 



