110 COMBINING PROPORTIONS. 



paratively rare occurrence. Combination between two ele- 

 ments is not known to occur in more complicated ratios than 

 the preceding, if the compounds *of carbon and hydrogen be 

 excepted, which are numerous and exhibit great diversity of 

 composition, like the compounds of organic chemistry gene- 

 rally, to which they properly belong. 



Combination likewise takes place among bodies which are 

 themselves compound, in proportional quantities,, which are 

 fixed, and determined by the law, that the combining number of 

 a compound body is always the sum of the combining numbers 

 of its constituents. Thus oil of vitriol, which is a combination 

 * of water and sulphuric acid, is composed of these bodies in the 

 proportion of 



Water . . 112.5 



Sulphuric acid . 501 



in which the combining proportion of the water (112.5) is the 

 sum of the proportions of its constituents ; namely, of oxygen 

 100 and of hydrogen 12.5; and that of sulphuric acid (501), of 

 those of sulphur 201 and of oxygen 300, there being three pro- 

 portions of oxygen in sulphuric acid. The combining propor- 

 tion of oxide of zinc is 503, the sum of oxygen 100 and zinc 

 403, and the compound of this oxide with sulphuric acid, or 

 the salt, sulphate of zinc, consists of 



Oxide of zinc . . 503 



Sulphuric acid . . 501 



1004 



Of potash, the combining proportion is 590, or oxygen 100 

 added to potassium 490, and to this proportion of potash the 

 usual proportion of sulphuric acid is attached in the sulphate of 

 potash, which is composed of 



Potash ... 590 



Sulphuric acid . 501 



1091 



Of these salts themselves, the combining proportions ought to 

 be the sums obtained by the addition of the numbers of their 

 constituents ; and accordingly the double sulphate of zinc and 

 potash consists of 



Sulphate of zinc . 1004 



Sulphate of potash . 1091 



2G95 



