the Diffusion of Gases. 251 



retical quantity. In another experiment with different gas, 

 the contraction was even greater, indicating a diffusion-volume 

 zr 1.0303 ; but the presence of a minute quantity of carbureted 

 hydrogen, or some lighter hydro-carburet, was suspected, from 

 the rapidity of the contraction in this case. 



13. Carbonic Oacide. Specific gravity, 0.9722, &c. as in the 

 case of nitrogen. Gas prepared by the action of sulphuric acid 

 on crystallized oxalic acid, well washed with caustic ley. 



On 803 measures carbonic oxide and vapour, a contraction of 

 11 measures in fifty hours, 12 measures in eighty-nine hours, 12 

 measures in ninety-seven hours ; or 803 became 791. The dif- 

 fusion was slower than usual, from the plug having been par- 

 tially wetted in filling the instrument with gas. 



R1 ^ 



ggg 1.0149 = diffusion-volume carbonic oxide, by experiment. 



1.0140zz diffusion- volume of carbonic oxide, by theory. 

 In the case of the last three gases, when the experiment was 

 performed over water in a diffusion-tube, with free exposure to 

 the dry atmosphere, instead of any contraction ensuing, a posi- 

 tive expansion generally occurred, which was to be attributed to 

 the return air, which was comparatively dry, being expanded af- 

 ter entering the receiver. 



14. Carbureted Hydrogen of Marshes. Specific gravity, 0.555, 

 Diffusion-volume, 1.3414. 



In an experiment with this gas, deducting a small quantity of 

 air which it contained, 252 measures were replaced by 187 air. 



r^ 1.344 diffusion-volume, by experiment. 

 1341 diffusion-volume, by theory. 



These are all the permanent gases which could conveniently 

 be submitted to diffusion. Vapours cannot be rigidly examined, 



