154 On the Chemical Constitution of 



thus a subnitrous acid is formed, which might afford the inter- 

 mediate proportion. Nitric oxide j;as, however, is disengaged, so 

 that there is probably no reduction in the degree of oxygenation. 

 And if tliere were, it would, conformably to tlie principle illus- 

 trated under the consideration of sulphuric acid, be replaced by 

 the oxygen of the base, and form the ternary compound consti- 

 tuting the nitrite, so that the relation of this element to the ni- 

 trogen would be the same. There is therefore no evidence of 

 the existence of any definite compound intermediate between ni- 

 trous 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 vvith a base ; for, as has been already shown, 

 when an acid yields water fiom 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 combination, in which the pro- 

 portion of oxygen to the radical remains the same. 



The real com])osition, therefore, must be determined in its state 

 of hydro-nitric 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 

 0"25 in acid of the specific gravity 1*50 be taken, this gives as 

 the composition 10 of nitrogen, vvith 40 of oxygen and 1*55 of 

 hydrogen: and this again gives 7 "S 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 ecjuivalent to 

 it,) thus assigned, is not the just proportion, essential to the con- 

 stitution 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 l'o2. At 1-50, therefore, it must be diluted 

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

 the common hyp:)thesis. Dr. Wollaston has observed, that to 

 decompose nitrate of potash so as to afford nitric acid, it is ne- 

 cessary to employ as much sulphuric acid as forms bi-sulphatc of 

 potash, and hence each portion of potash from which dry nitric 

 acid is separated, will displace the water from tvvo equivalents of 

 sulphuric acid. One of these portions of water, it may be pre- 

 sumed then, will go as essential to the constitution of the i:itric 

 acid^ or rather its oxygen and hydrogen will do so ; the other is 



adventitious, 



