SPECIFIC GRAVITY OF OXYGEN GAS. 65 



But if it were in the gaseous state, we know 

 that its volume would be just half that of the 

 hydrogen gas, or 69*3775 cubic inches. Thus 

 it appears, that 100 grains of zinc, when con- 

 verted into an oxide, unite with 69*3775 cubic 

 inches of oxygen gas. 



But from the facts established in the last sec- 

 tion, it is evident, that 100 grains of zinc, when 

 converted into an oxide, combine with 23*5294 

 grains of oxygen.* Hence, the weight of 69*3775 

 cubic inches of oxygen gas is 23*5294 grains. 

 Consequently, 100 cubic inches weigh 33*915 

 grains.t 



From the experiments of Sir George Shuck- 

 burgh Evelyn we learn, that 100 cubic inches 

 of dry common air, under the same pressure, 

 and at the same temperature, weigh 30*5 grains. 

 And the specific gravity of common air being 

 always reckoned unity, it is obvious that the 

 specific gravity of oxygen gas must be l*llll.t 



Thus we have obtained by a very simple pro- 

 cess, which does not seem liable to any uncer- 

 tainty, the very specific gravity of oxygen gas 

 which Dr. Prout deduced from the supposition, 

 that air is a mixture of four volumes azotic, and 

 one volume oxygen gas ; and which I adopted in 



* 4-25 grains of zinc unite with 1 grain of oxygen, and 4-25 : 1 : : 100 : 

 23-5294. 



f For 69-3775: 23-5294 : ; 100 : 33 915. 

 t For 30-5 : 33-915 : : 1 : Mill nearly. 

 VOL. I. E 



