the Diffusion of Gases. 243 



An expansion took place of 4 measures in ten minutes, and 

 of 40 measures in five hours. A standard tube of the same dia- 

 meter as the diffusion-tube, sealed at the top, had been filled with 

 carbonic acid and placed over brine, to mark the absorption of 

 the gas. One measure of gas was absorbed during the continu- 

 ance of the above experiment. The expansion, therefore, in the 

 diffusion-case has really been 41 and not 40, or, probably even 

 more than 41, as undoubtedly a greater absorption of gas by the 

 brine occurred in the diffusion-tube than in the standard-tube, 

 from the motion of the liquid in the former during the course of 

 the expansion of its gaseous contents, while the liquid in the 

 other was quite at rest, and 177.6 1 ,or 176.6 carbonic acid gas 

 only have been exposed to diffusion. The diffusion was allowed 

 to take place into the open air, which had the same proportion 

 of vapour as the carbonic acid. 



The specific gravity of carbonic acid gas is 1.527, of which 

 the square root is 1.2360, and the reciprocal of the square- root 

 0.8091. Hence one volume air should replace 0.8091 carbonic 

 acid gas, which is the theoretical diffusion-volume of this gas. 



In the experiment, 176.6 carbonic acid are replaced by 

 217.6 air. 



Here, the expansion upon 1 76.6 carbonic acid being replaced 

 by air is 41 + parts by experiment, while it is 41.68 parts by 



theory. 



The diffusion^ volume of carbonic acid gas is, 

 0.812 by experiment, 

 0.809 by theory. 



Experiment 2 In another experiment, conducted in the 

 same manner, thermometer 64, barometer 30.00, the initial con- 

 tents of the diffusion-tube were, 



Carbonic acid and vapour, 201. 

 The final contents, 







Air and vapour, - - 245. 



