The Action of Metals, &c., on India-rubber. 279 



Action of Acids on India-rubber, 



We have heard it asserted, from time to time, that a 

 trace of sulphuric acid contained in india-rubber would soon 

 determine its decay and decomposition. With a view to 

 testing this point we took different acids, which were all 

 brought to the same strength, viz., that 100 parts of the 

 different acid solutions neutralized 100 parts of a 10 per 

 cent solution of anhydrous sodium carbonate. These acids 

 were placed in stoppered bottles, two bottles being half-filled 

 with each acid solution, into each of which was immersed a 

 thin sheet of rubber on paper as above described, about 2 J^ 

 inches square ; one of each was placed in the incubator and 

 kept at 140° Fah. for a month, and the other kept during 

 that time in the cold, the rubber in each being tested from 

 time to time to ascertain whether the acids had any effect 

 upon the sheets. The following acids were employed : — 



Hydrochloric Acid. 



Sulphuric 





Nitric 





Chromic 





Citric 





Tartaric 





In the first four, the paper in the heated samples to 



which the fine sheet rubber was adhering was soon reduced 



to a pulp, leaving the sheet of rubber intact. After a few 



hours it was evident that the rubber in the nitric acid placed in 



the incubator had been seriously damaged, and after a few 



-days it was so acted upon that its elasticity was destroyed, 



and after a month the whole of the rubber was reduced to a 



pulp, whilst at the end of the month the sheets of rubber in all 



the other acids remained as strong and elastic as they were 



on being first immersed. The sulphuric acid solution 



which had been heated in the incubator had darkened the 



colour of the rubber, but so far as we could judge by 



