Prof. Graham on the Law of the Diffusion of Gases. 273 



it contained, 51 measures were replaced in ninety minutes by 

 62 dry air. Taking the specific gravity of this gas at 1*2577, 

 its root is 1*2360, of which the reciprocal is 0*8091. 

 Diffusion-volume 0*82 by experiment, 

 0*81 by theory. 



6. Cyanogen. — Also over mercury. First deprived of hy- 

 drocyanic acid by peroxide of mercury, and dried, an expan- 

 sion always resulted from diffusion, but it never amounted to 

 the theoretical quantity. Taking 1*8105 as the specific gra- 

 vity of cyanogen, the square root is 1*3456, and the reciprocal 

 of the square root 0*7432. 



Hence, 1 cyanogen is replaced by 1*3456 air; and 

 1 air replaces 0*7432 cyanogen. 



1st, 83 cyanogen were replaced by 99^ air; 2nd, 75 cyano- 

 gen by 90 air ; 3rd, 50 cyanogen by 63 air. The last experi- 

 ment is the most favourable. But 100 cyanogen are replaced, 

 according to that experiment, by 126 air only, instead of 134. 

 This deviation from the law, depends on the property of the 

 plaster-plug, which it shares with all porous bodies, to absorb 

 and condense a portion of all those gases which, like cyanogen, 

 are easily liquefied. It is evident, that if a portion of the cyano- 

 gen is withdrawn in this way, a certain contraction is occa- 

 sioned, and again really less of the gas is submitted to diffu- 

 sion ; and from both causes, the expansion is less than it ought 

 to be. It is possible, also, that the cyanogen may have con- 

 tained a little nitrogen. 



7. Muriatic Acid Gas. — Specific gravity 1*28472; square 

 root, 1*1334; reciprocal of square root 0*8823. Hence, 



1 muriatic acid should be replaced by 1*2847 air; and 

 1 air should replace 0*8823 muriatic acid. 

 In the case of this gas, the expansion from diffusion was 

 overpowered by the absorbent property of the plug. 



94 measures contracted to 88 in ten minutes, and remained 

 at that quantity for nine minutes, and then expanded to 90 

 measures in twenty-five minutes more. The plug, upon a 

 subsequent examination, appeared to be injured, and rendered 

 too permeable, by a chemical action of the muriatic acid upon 

 the hydrated sulphate of lime. 



8. Ammoniacal Gas. — Density 0*5902. Square root 0*76825; 

 reciprocal of square root 1*3016. Hence, 



1 ammoniacal gas should be replaced by 0*76825 air; and 



1 air should replace 1*3016 ammoniacal gas. 



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 



Third Series. Vol. 2. No. 10. April 1833. 2 N 



