a New Class of Salts, 215 



would have corresponded to 12 equivs.; 11 equivs. would yield 

 a loss of 10*6 per cent, 



Nitroprusside of Barium, 



13. This salt is obtained by decomposing nitroprusside of 

 copper by caustic barytes, avoiding an excess of the latter. 

 On filtration a dark red-coloured solution passes through. 

 When evaporated under the air-pump, it forms fine large 

 pyramidal crystals. The following measurements have been 

 made by Prof. Miller of Cambridge : — 



Symbols:— -a 100, c 001, r 111. 



Angles between normals to the faces : — 



ac 90 

 aa' 90 

 re 44 35 

 ri^ 59 30 

 ra 60 15 



This salt, out of a strong solution, also frequently crystal- 

 lizes in flattened prisms ; no doubt as a different hydrate. 



Nitroprusside of barium is of a dark red colour, is easily 

 soluble in water, and is not deliquescent. It deposits a brown 

 precipitate on boiling, resembling oxide of iron, but which, in 

 the specimen examined, also contained barytes. The salt, 

 after it has experienced this change, crystallizes in the same 

 form, but with impurities which cannot be separated by filtra- 

 tion or crystallization. Analyses of this altered salt are given 

 in a subsequent part of this paper. 



The salt crystallized in the air-pump lost water in water- 

 bath. 



20-415 grs. lost at 212° 3-110 grs. water =15-233 per cent. 

 24-455 grs. lost at 210° 3-648 grs. water =14-917 per cent. 



The analyses were made by acting upon the salt by sul- 

 phuric acid in the usual way. \^ 



I. 20*791 grs. gave 12*173 grs. sulphate of barytes and 4-180 



grs. oxide of iron. 

 II. 17-24 grs. gave 10-198 grs. BaO, SO^ and 3-48 Fe^O^. 



The combustions were made with chromate of lead. 



I. 8-539 grs. gave 1-208 gr. water and 4-665 grs. carbonic 

 acid. 

 II. 10068 grs. gave 1*132 HO and 5-580 CO^. 



