292 Dr. Murray on the Chemical Constitution of [Oct. 



pounds, and must contribute greatly, independent of uniformity 

 and simplicity, to vender that of the former, at present so involved 

 in obscurity and discordance, more precise. 



The compounds of nitrogen with oxygen present considerable 

 difficulties ; some of them are not easily obtained insulated ; the 

 specific distinctions, therefore, which constitute the series, have 

 been variously represented, and the subject is still imperfectly 

 elucidated. Two of them, however, are determined with suffi- 

 cient precision, from which we may proceed — those constituting 

 the two oxides ; the first, nitrous oxide, being composed of 10 

 of nitrogen with 5*7 of oxygen; the second, nitric oxide, of 10 

 of nitrogen with 1T4 of oxygen. 



These combinations are conformable to the usual law of defi- 

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

 other as 2 to 1. It might be expected, therefore, that in the 

 two succeeding compounds admitted by chemists, nitrous and 

 nitric acids, the same, ratio would be observed ; that the oxygen 

 in the one Avould 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 beipg 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 accu- 

 racy the proportions may be fixed at 1 of nitrogen with 28-5 of 

 oxygen — a proportion of oxygen 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 oxygen, which makes the multiple of oxygen 7 — a 

 result equally distant from the regular progression. 



The composition of the 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 

 intermixture of nitric acid and nitric oxide. Different views 

 have been proposed with regard to it to remove the difficulty. 

 Gay-Lu^sac, in particular, assumed the existence of two com- 

 pounds; p^vnitrous and nitrous acid, intermediate between nitric 



