226 PROCEEDINGS OP THE AMERICAN ACADEMY 



Tare of Empty Balloon. 



Values. 



A 2.5098 grams. 



B 2.5573 " 



C 2.5480 " 



Density of Air freed from Moisture and Carbonic Acid. 



In these determinations the balloon was placed in the calorimeter 

 case and connected with the Bunsen pump through an overflow jar. 

 Air was then drawn into it through the purifiers we have described, 

 and the reflux current which followed for a moment when the inlet 

 cock was closed was supplied from the previous overflow. In other 

 respects the determinations were made as before described, and we 

 obtained the following data for the weight of air held in the balloon 

 at different temperatures and pressures. 



Summary of Air Weights. 



A No. 1, weight of air at 762.63 mm. and 18°.52 = 6.0347 grams. 

 A No. 2, " " 758.71 " " 19°.96 = 5.9745 " 



B No. 1, " " 750.30 " " 23°.32 = 5.8411 " 



Reducing now these weights to what they would have been at the 

 temperatures and pressures we have assumed as standards, we obtain 

 the following comparable values. 



, Reduced Air Weights for 



H == 761.99 mm. = 300 d. in* and 



T = 27° C. = 300° absolute temperature. 



A No. 1 5.8584 grams. 



A No. 2 5.8588 " 



B No. 1 5.8586 " 



Average value 5.8586 grams, t 



* We shall use the abbreviation d. in. for tenths of an inch, after the analogy 

 of d. m. for tenths of a meter. 



t In the calculations of density and specific gravity, a still further, although 

 wholly unimportant, correction has been made for the buoyancy of the air on 

 the brass weights used to complete the tare in weighing the balloon, and in this 

 connection it must be borne in mind that the platinum or aluminum fractions of a 

 gram in a set of weights have always been adjusted to the larger brass weights 

 in the air, and are therefore the equivalent of brass weights of the same denomi- 



