conformity with the Dynamical Theory of Heat and Gases. 251 



From these two equations we have y = lj and x=%; and phos- 

 phoretted hydrogen is represented by H^P*, which signifies 

 that a gaseous molecule of phosphoretted hydrogen is composed 

 of 1| gas-molecule of hydrogen united to one-quarter of a 

 gaseous molecule of phosphorus. In the sesquichloride of phos- 

 phorus the weight of phosphorus is to the weight of chlorine as 



Vx 1 64.r 



1 to 3-375, hence ^r- = - y = ^-. The vapour-density of 



the compound is 70 = Vx + C\z = 64^ + 362". Prom these two 

 equations x comes out = ^, and s = l §. Hence Pi CI 1 * expresses 

 the constitution and vapour-density or weight of a gaseous mole- 

 cule of the sesquichloride. Thus the combining element or 

 chemical atom of phosphorus is still one-quarter the gaseous 

 molecule. 



In the preceding examples the smallest combining element of 

 chlorine is half the gaseous molecule. It combines also in the 

 proportion 1, 1|, and 2 gaseous molecules. 



The smallest combining element of hydrogen is half the 

 gaseous molecule. It combines also in the proportion \ i \\ ) % 

 gaseous molecules ; and further, in the organic compounds its 

 combining proportions extend up to 16 gaseous molecules, as in 

 petrolin or colophon, H 16 C 10 . 



The smallest combining element of oxygen is one-half the 

 gaseous molecule. It combines also in the proportion 1, 1|, 2, 

 "2\, 3 gaseous molecules: e.g. an arsenious acid vapour-molecule 

 is composed of one arsenic vapour-molecule united with three 

 oxygen gas-molecules. 



Muriatic acid gas, CI* H*, is composed of single half molecules 

 of its constituents united together. 



Cyanogen, NC, is composed of whole single molecules of its 

 constituents united together ; and this compound molecule 

 assumes the deportment of a chemical element by splitting into 

 two in some of its combinations with hydrogen, &c, as N*C*Hi, 

 prussic acid ; N* C* CI*, chloride of cyanogen ; and N* C* Br*, 

 bromide of cyanogen. 



In silicated hydrogen the ratio of hydrogen to silicon is- = ^~ , 



7 Si. x 

 H = l, Si= ?, Si . H= ?. Hence there are no data to computer 

 andy. By analogy we might infer Si =28; and if Si a? Hz/ =16, 

 we should have # = |- and y=2 ; and silicated hydrogen, Si* H 2 , 

 homologous with marsh-gas, C2 H 2 . 



In ammonia the ratio of hydrogen to nitrogen is 1 to 4*67, or 



N^ = 4^7* ^he specific gravity of the gas being 8*5 = No; + Hy, 



