78 COMBINING WEIGHTS. " 



pounds consist of a single proportional of each of 

 these elements, but more commonly they contain one 

 of one element, and two, three, or more of the other; 

 of-ganic substances, for the most part, consist of 

 nearly ten or a dozen proportionals of each of their 

 elements (316, 369). 



142. The following table shows the proportions or 

 combining weights of the most important simple sub- 

 stances. 



Oxygen 8 



Hydrogen 1 



Carbon 6 ^ 



Nitrogen . . . . . . . 14 



Chlorine 35 



Phosphorus 31 



Sulphur . . . . . . .16 



Iron 27 



143. When a compound is formed by the union of 

 two elements, the equivalent or combining proportion 

 of the compound is exactly the sum of the equivalent 

 of its elements; thus, for example, carbonic acid con- 

 sists of one equivalent of carbon, the number of which 

 is 6, and two equivalents of oxygen, weighing 16 ; the 

 sum of 6 and 16, is 22 ; this, then, is the equivalent 

 of carbonic acid, the quantity which will combine with 

 an equivalent weight of any base, for example, with 

 28 parts of lime, 47 of potash, and so on. 



144. In the following table the combining weight 

 of some of the most important compounds is exhi- 

 bited : — 



