250 Mr. J. J. "Waterston on Chemical A otation in 



TT -l 



have Hy + C^=8 and — - = 5 '» substituting 1 = H and 12 = C, 



y 1 

 we have y + 12cc= 8 and -~~ = a- From these two simple equa- 



tions we find oo=^\ and y=2. Hence marsh-gas is expressed 



by C^ + H2 = C * H 2 , which means that a gaseous molecule of 



marsh-gas is composed of half a molecule of carbon united to 



two gaseous molecules of hydrogen. 



In monochloromethene, or muriate of methyle, the ratio of the 



H?/ v 

 hydrogen to the carbon is — = ~- = -~~. The ratio of the hy- 



1 Hy y 

 drogen to the chlorine is r— = ~- = ^-, and the vapour-den- 

 sity of the compound is 



25i = Hy + Ca? + CLsr=y + 12^ + 36^. 

 Erom these three equations we find x — z — J and y — \\. Hence 

 this compound is expressed by HlJ-f C| + Cli = H^C^Cl^ 

 which means that its vapour-molecule is composed of one and a 

 half gaseous molecules of hydrogen, half a molecule of carbon, 

 and half a gaseous molecule of chlorine united together. 



In the same way dichloromethene, or chloride of methyle, is 

 expressed by HO CI, the vapour- density being 



ao_ fH + C^ + Cl 

 * 6 ~ \l +6 +36' 



and chloroform by H^ C^ Cl 1 ^, its vapour-density being 



eoi-IHUc^+ci 1 *. 



*~ U + 6 +54 ' 

 and the tetrachloromethene, or perchloride of muriate of methyle, 

 by C^ CI 2 , its vapour-density being 78. 



Following the same system, water is expressed by 



h°<— {?:?. 



its vapour-molecule being composed of one gas-molecule of 

 hydrogen united to half a gas-molecule of oxygen. 



Phosphoretted hydrogen consists of one part by weight of 



hydrogen united to 10*5 phosphorus, or ~- = tttf, and its 



vapour-density is 17'5 = Ky + Voc. The vapour- density of phos- 

 phorus being 64 =P, we have 



6^ = 1^5 and ^ + 64 *= 17 ' 5 - 



