228 PEOCEEDINGS OP THE AMERICAN ACADEMY 



Specific Gravity of Hydrogen. 



Air = 1. 



The values were obtained by dividing each of the weights of hydro- 

 gen above given by the average weight of air (5.8586), after reduction 

 for the temperatures and pressures at which the hydrogen weights 

 were observed. The calculations were verified by dividing each of 

 the reduced weights of hydrogen by the average reduced weight of 

 air as above, and the same figures were obtained in both ways. 



B No. 1 0.06957 



B No. 2 ■ 0.06951 



B No. 3 0.06966 



Average 0.06958 



Average using values of tare by chemical method 0.06962 



Specific Gravity of Oxygen. 



Hydrogen = 1. 



In this investigation we have not made an additional determination 

 of the specific gravity of oxygen gas referred to air, for the causes of 

 error which are serious in the case of hydrogen are not appreciable 

 when working with the heavier gas, and we cannot expect to improve 



the last decimal place ; and in this paper, as is usual, the decimals are carried 

 out one figure beyond the limits of accuracy. 



In tlie chemical method we also took the weight of the balloon filled witli 

 carbonic acid gas, and, as before, we have 



W" = 2.5573 ± w + 8.9564 - w'". 



Then by chemical means we determined the absolute weight (in vacuo) of 

 I lie carbonic acid which tlie vessel held, that is, the quantity represented by 

 8 9564 — w'". Subtracting this value from the total weight, we obtained the 

 tare of the empty balloon by the chemical method, and this obviously is 



Wc = 2.5573 ± w. 



Thus, the buoyancy of the air on the weights is eliminated, and Wc is directly 

 comparable in all its relations with Wr. 



