402 



ME. T. GEAHAM ON THE ABSOEPTION AND 



and transpiration-experiments, for reasons which will immediately appear, yet they give 

 a comparative estimate of the penetrativeness of the different gases through rubber, 

 which may be available for some practical purposes. 



Upon another occasion carbonic oxide and marsh-gas (C H^) were introduced into the 

 comparison, the same film of rubber remaining upon the diffusiometer ; barom. 768 

 millims., therm. 19°-5 C. 



Table III. 



The results may be summed up by deducing the times in which a constant volume of 

 the various gases is transmitted by the rubber, the time of passage of carbonic acid, 

 which is the shortest, being taken as unity for the sake of comparison. 



Penetration of rubber by equal volumes of Gas. 



Time. 



Carbonic acid ....... 1 



Hydrogen 2-470 



Oxygen 5'316 



Marsh-gas (CH4) 6-326 



Atmospheric air 11-850 



Carbonic oxide 12-203 



Nitrogen 13-585 



Or, with the times taken equal, the volume of each gas which passes then expresses the 

 velocity of penetration. 



Penetration of rubber in equal times. 



Velocity. 



Nitrogen 1 



Carbonic oxide 1-113 



Atmospheric air 1-149 



Marsh-gas (CHJ ....... 2-148 



Oxygen 2-556 



Hydrogen 5-500 



Carbonic acid 13585 



