

Prof. Graham on the Law of the Diffusion of Gases. 271 



Carbonic acid and vapour, 201. 

 The final contents, 



Air and vapour 24-5. 



Correcting for loss of gas by absorption, the final contents 

 would be, Air and vapour 24-6. 



As the proportion of vapour in the gas at the first, and in 

 the air finally is the same, we may say that carbonic acid is 

 replaced by air in the proportion of 201 to 246. 



201 



— — = 0*813 = diffusion- volume of carbonic acid. 



24<6 



Exp. 3. — In a third experiment over brine, thermometer 



62°, barometer 29*65, carbonic acid and vapour 169 



Replaced by air and vapour 205 



Or, allowing for absorption, by air and vapour 206 



169 



— — = 0*816 = diffusion-volume of carbonic acid. 



zuo 



But extreme accuracy is quite out of the question in the 

 case of carbonic acid, from the vagueness of the small correc- 

 tion for absorption of the gas by the brine, and from the ab- 

 sorbent action of the plug, which affects, more or less, all the 

 condensible gases. 



The experiment in the case of this gas had been performed 

 repeatedly over water itself, in different diffusion-tubes, and 

 always with an eventual increase to the gaseous contents of 

 the tube of within 2 per cent, of the theoretical quantity; but 

 this mode, and the corrections for absorption, are decidedly 

 inferior in precision to the preceding. 



3. Chlorine. — This gas, from its high density, should afford 

 a good illustration of the law, were other circumstances equally 

 favourable, as the specific gravity of chlorine is about 2*5, of 

 which the square root is 1*5811, and the reciprocal of the 

 square root 0*6325. 100 measures of chlorine should be re- 

 placed by 158*11 air; or 1 air should replace 0*6325 chlorine, 

 which is its diffusion-volume. 



Experiment. — Thermometer 64-°. To a diffusion-tube over 

 water, with 5 measures air, 80 chlorine gas were added, ma- 

 king together 85 measures, which, diffusing into damp air, 

 expanded 3 measures in the first eight minutes, 18 measures 

 in eighty-two minutes, and, finally, 19 measures in one hun- 

 dred and six minutes; but the same gas, in a close standard 

 tube of the same diameter, contracted, owing to absorption 

 of the gas by water, 5 measures in eight minutes, 15 mea- 

 sures in thirty-three minutes, and 18 measures in thirty-nine 

 minutes, the rate of absorption diminishing evidently from the 



