COMBINING QUALITIES. 43 



by which is to be understood, in the words 

 of the law, that " certain definite quantity " in 

 which, and in none other, will it unite with 

 other elements. These proportions or equiva- 

 lents are all different from each other, though 

 some approach remarkably close to a common 

 number ; thus, the " equivalent " of carbon is 6 ; 

 that of lithium 6'43. 



3rd. When a chemical body, say oxygen, 

 unites with another in several quantities or 

 proportions, or " equivalents," these propor- 

 tions bear a simple relation to each other. 



For example : Oxygen unites with nitro- 

 gen in five different quantities, or proportions, 

 thus : 



Nitrogen 14 unites with 1 oxygen or 8 parts by weight. 

 2 oxygen or 16 



3 oxygen or 24 



4 oxygen or 32 



5 oxygen or 40 



In this table, while the proportion of nitrogen 

 remains constant, that of oxygen increases in 

 the simple ratio of 8, 1.6, 24, 32, 40. 



4th. The combining quantity, or " equiva- 

 lent" of a compound substance, is the sum of 

 the combining quantities of its component ele- 

 ments. 



For example : is itric acid, without any water 

 in its composition, is composed of fourteen 



