1819.] Acids, Alkalies, and their Compounds. 29U 



oxide and nitric acid, which, from their proportions, afforded the 

 intermediate multiples 3, 4, that of real nitric acid being consi- 

 dered as 5. But Dulong has shown that these acids are the 

 same. He has also obtained nitrous acid in its insulated state ; 

 its composition is 10 of nitrogen with 22-8 of oxygen — a propor- 

 tion of oxygen which gives the multiple 4 ; so that the series is 

 still incomplete, being that of 1, 2, 4, and either 5, or 7. 



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 

 nitrate ; and the other forms a nitrite. It might be supposed, 

 therefore, that one portion of it yields oxygen to the other, and 

 that thus a subnitrous acid is formed, which might afford the 

 intermediate proportion. Nitric oxide gas, however, is disen- 

 gaged, so that there is probably no reduction in the degree of 

 oxygenation. And if there were, it would, conformably to the 

 principle illustrated under the consideration of sulphuric acid, be 

 replaced by the oxygen of the base, and form the ternary com- 

 pound constituting the nitrite, so that the relation of this element 

 to the nitrogen would be the same. There is, therefore, no 

 evidence of the existence of any definite compound intermediate 

 between nitrous acid and nitric oxide, and the ratio of oxygen in 

 nitrous oxide and these two compounds is that of 1, 2, 4. 



The proportion in nitric acid, it has been stated, is that which 

 gives the multiple 5 of oxygen. But this applies to what is 

 called the real acid free from water, and no such compound 

 exists, not even in combination with a base ; for, as has beea 

 already shown, when an acid yields water from the action of a 

 base, though there is thus an abstraction of a portion of its 

 oxygen, it receives that of the base, and forms a ternary combi- 

 nation, in which the proportion of oxygen to the radical remains 

 the same. 



The real composition, therefore, must be determined in its 

 state of hydronitric acid. The quantity of combined water, 

 according to the common expression of the fact, existing in it. 

 has been variously stated ; but if the estimate in Dr. Wollaston's 

 scale of 025 in acid of the specific gravity T50 be taken, this 



fives as the composition 10 of nitrogen, with 40 of oxygen and 

 •55 of hydrogen : and this again gives 7 as the multiple of 

 oxygen in the series of compounds — a result which it is scarcely 

 possible to connect according to the established law with the 

 multiple 4, in the lower compound, nitrous acid. 



It is certain, however, independent of this circumstance, that 

 the quantity of water (or of oxygen and hydrogen equivalent to 

 it;, thus assigned, is not the just proportion essential to the 

 constitution of the acid ; for the specific gravity 1*50 is not the 

 highest at which it can be procured. It is obtained with cer- 

 tainty at 1-55 at 60° ; by some chemists it is stated at 1*58, and 

 by Proust even at 1*62. At 1*50, therefore, it must be diluted 

 with a certain portion in addition to the real combined watev of 



