248 Mr GRAHAM on ike Law of 



But in the case of this gas, as with muriatic acid, the result of 

 diffusion is altogether deranged by condensation of gas in the 

 porous plug, which, in these experiments, was half an inch in 

 thickness. It is remarkable, however, that, when the tube was 

 filled with ammoniacal gas in the usual way, the final contraction 

 was by no means excessive, indeed, never quite so great as it 

 should have been from diffusion alone, independently of the con- 

 traction from absorption. This was found to arise from the ab- 

 sorption by the plug being so rapid, that, during the progress of 

 filling the tube with gas, the plug became nearly saturated with 

 gas, taking up ten or twelve times its bulk, and, consequently, a 

 great deal more gas was introduced into the tube than its capa- 

 city. 



9. Sulphureted Hydrogen Gas. Prepared from sulphuret of 

 antimony, by the action of muriatic acid. Density, 1.1805. Root, 

 1.0855. Reciprocal of root, 0.9204. 



In the case of this gas, 69 measures were replaced by 73 air. 

 In this experiment, 100 air replaced 95 instead of 92 sulphu- 

 reted hydrogen. But we may refer the diminution to the ab- 

 sorption of the gas by the plug, and to its partial decomposition, 

 as the mercury exposed to the gas became black. The air which 

 entered contributed to this decomposition. 



As carbonic acid is one of the gases condensed by the plug, 

 like the preceding examples, but to a less extent, we can now 

 understand why the return air was always a little under the theo- 

 retical quantity, in the careful experiments on that gas, of which 

 an account was formerly given. 



In the case of the gases which follow, the specific gravity ap- 

 proaches so closely to that of air, that their accordance with the 

 law requires every precaution. 



1 0. Oxygen Gas. Specific gravity, 1.111. Square root, 1 .054 1 . 

 Reciprocal, 0.9487. 



