Hartley — On the Constitution of Nitric Acid and its Hydrates. 375 



The above acids were isolated as crystalline solids with low 

 melting points, capable of being distilled unchanged under 

 diminished pressures, and under these conditions maintaining 

 the character of definite stable compounds. 



At - 15° orthonitric acid, N(OH) 5 is produced from either 

 stronger or weaker acid by passing a current of dry air through it. 

 The solutions of nitric acid in which several hydrates were recog- 

 nised by their absorption spectra are shown in the following 

 table : — 



Hydrates of Nitric Acid. 



The important work of Yeley and Manley (Proe. Roy. Soc, 

 1901-2, 69, pp. 86-119) by curves of densities and curves of con- 

 tractions shows the existence of compounds formed in solutions 

 when the ratios are HN0 3 : 14, 7, 4, 3, 1*5, and 1 H 2 0, and by 

 refraction indices with ratios HN0 3 : 14, 7, and 1*5 H 2 0. From 

 these measurements we get the following hydrates and acids: — 

 N(OH) 5 • 12H 2 0, N(OH) 3 ■ 5H 2 0, (HO) 4 N ■ O ■ N(OH) 4 , 

 N (OH) 5 * 2H 2 0, N (OH), • H 2 0, ON(OH) 3 . 



Both Pickering's curves and those of Veley and Manley 

 indicate in a remarkable degree the existence of the octobasic 



SCIENT. PR0C. R.D.S., VOL. X., PART III. 



2 H 



