Mr. R. Phillips on Nitric Acid, S^c. 429 



digested in water, and the precipitate collected on a filtre. The 

 solution which passed through had a deep red colour, and on 

 cooling deposited crystals of a fine grass-green colour in the 

 form of oblique rhombic prisms, with the acute angles trun- 

 cated just like the salt obtained from the sulphate of zinc; and 

 on analysis it proved to be very similarly composed, for by 

 the above process it afforded the following results : 



Sulphuric acid 18-260 



Chromic acid '978 



Oxide of nickel 8-200 



Potash 9-862 



Water 12-700 



50-000 grains. 



A similar salt may be obtained by mixing chromate of pot- 

 ash and sulphate of coppei*. It is of a light green colour, and 

 has precisely the same form as the salts already described. In 

 every instance after the first crop of crystals had been re- 

 moved, and the solution further evaporated, bichromate was 

 formed. 



The crystalline form of all these salts appeared to be the 

 same. The annexed figure 

 represents their shape ; they 

 are pretty soluble in water, 

 and undergo no change from 

 exposure to the atmosphere. 

 What appears most remark- 

 able about these salts, is 

 the small quantity of chromic acid which they contain; and in 

 this respect they seem to have some analogy to the orange 

 phosphate of lead described by Mr. Vernon in the Philosophi- 

 cal Magazine for May last. 



As these salts, as far as I know, have never been described, 

 and as Dr. Thomson appears to mistake their nature, I pub- 

 lish this brief notice of them now, although it is two years 

 since I first prepared them. 



Dublin, Oct. 2, 1827. 



LXXIII. On Nitric Acid, and on a peculiar Sulphate of Potash. 

 By R. Phillips, F.R.S. L.SfE. 



tTAVING lately had occasion to attend to the preparation 

 ■*■-*• of nitric acid, some circumstances occurred with respect 

 both to the acid and the residual salt, which have not, I be- 

 lieve, been noticed by any chemical author. Intending to pre- 

 pare 



