Acids, Alkalis, and their Compounds. 1 83 



nite proportions, tlie oxygen in the one being to that in the other 

 as 2 to 1. It might be expected, therefore, that in the two suc- 

 ceeding compounds admitted by chemists, nitrous and nitric acids, 

 the same ratio would be observed; that the oxygen in the one 

 would be as 3, and in the other as 4. It appears, however, from 

 experimental evidence, that these are not the proportions. 



Nitric acid, the extreme of the series, is the one most capable 

 of being obtained uniform, and the composition of which admits, 

 therefore, of the most exact determination. Even with regard 

 to it there are discordant results; but from those of greatest ac- 

 curacy the proportions may be fixed at 10 of nitrogen with 28*5 

 of oxygen, — a proportion of oxvgen which is to the first not the 

 multiple of 4, but 5, and which therefore breaks the uniformity 

 of the series. 



The composition thus assigned, however, is that of what is 

 called real nitric acid, free from the portion of combined water 

 supposed to exist in the acid in its insulated state, and abstracted 

 when it passes into its saline combinations. If we exclude this 

 hypothesis, and consider this water as existing in the acid in the 

 state of its elements, and the acid, therefore, as a ternary com- 

 pound of nitrogen, oxygen, and hydrogen, this portion of oxygen 

 is of course to be admitted into the calculation. But still this 

 does not obviate the difficulty. The quantity of this water has 

 been variously estimated. If the estimate by Dr. Wollaston be 

 admitted, that of 0-25, it gives the proportion of 10 of nitrogen 

 and 40 of oxvgen, which makes the multiple of oxygen 1 , a re- 

 sult equally distant from the regular progression. 



The composition of tlie intermediate compound, nitrous acid, 

 it has been found still more difficult to determine, principally from 

 the difficulty of obtaining it insulated, and free from all inter- 

 mixture of nitric acid and nitric oxide. Different views have 

 been proposed with regard to it to remove the difficulty. Gay- 

 Lussac, in particular, assumed the existence of two compounds, 

 pernitrous and nitrous acid, intermediate between nitric oxide 

 and nitric acid, which, from their proportions, afforded the in- 

 termediate multiples o, 4, that of real nitric acid being considered 

 as '). But Dulong has shown that these acids are the same. He 

 has also obtained nitrous acid in its insulated state; its compo- 

 sition is 10 of nitrogen with 22-8 of oxygen; a proportion of 

 oxygen which gives the nuiltiple 4, so that the scries is still in- 

 complete, being that of 1, 2, 4, and either 5, or 1 . 



When this acid is acted on by an alkaline base it is decom- 

 posed, one part passes to the state of nitric acid, and forms a ni- 

 trate, and the other forms a nitrite. It might be supposed, there • 

 fore, that one portion of it yields oxvgen to the other, and that 

 M 4 ' thus 



