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XXXIII. 



NOTES ON THE CONSTITUTION OF NITEIC ACID AND 

 ITS HYDRATES. 



By WALTER NOEL HARTLEY, D.Sc, F.R.S. 



[Read, April 18 ; Received for Publication, April 20 ; Published, June 19, 1905.] 



It has already been shown that the spectra photographed through 

 definite thicknesses of nitric acid of different strengths afford 

 direct evidence of the existence of a compound with the formula 

 H3NO4 • H 2 termed orthonitric acid from analogy with ortho- 

 phosphoric acid, and, in addition, of several hydrates formed in 

 solution until the molecular proportions were HN0 3 : 14H 2 0. 

 (Chem. Soc. Trans., 1903, 83, 658.) When studying the reactions 

 of some of the acids, the spectra of which had been photographed, 

 a paper by H. Erdmann of remarkable interest came under my 

 notice, to which I beg leave to draw attention (Ueber Orthosalt- 

 petersaure N(OH) 5 und die durch Wasserabspaltung daraus 

 entstehenden Yerbindungen. Zeit. f. Anorg. Chem., 1902, 32, 

 pp. 431-36). It is stated therein that Mitscherlich believed he 

 had prepared an acid of the composition required by the formula 

 N(OH) 5 , and Wislicenus was of opinion that this acid was a stable 

 compound at low temperatures. Further important evidence of 

 its existence was obtained by Pietet and Genequand (Ber. Deutsch. 

 Chem. Gresellsch., 1902, 35, p. 2526) by preparing a diacetyl 

 derivative by the interaction of equal volumes of acetic anhydride, 

 and nitric acid, of sp. gr. 1*4. The action is more under control 

 if glacial acetic acid and fuming nitric acid of sp. gr. 1'52 are 

 employed. 



The new compound is not decomposed on distillation, it boils 

 at 1277 at 730 mm., and its formula is (CH 3 • COO) 2 N(OH) 3 ; 

 thus the existence of the acid N(OH) 5 is satisfactorily established 

 by a definite chemical reaction. Erdmann obtained this acid 

 crystallized in long needles which melt at - 35° ; it boils under a 

 pressure of 13 mm. at from 40° to 40*5°, undergoing dissociation, 

 but it is a stable substance at - 15°. My observations showed 



