492 
DR. PLAYFAIR ON THE NITROPRUSSIDES, 
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 1 1 1. 
Angles between normals to the faces : — 
ac 90 0 
aa! 90 0 
rc 44 35 
rr' 59 30 
m 60 15 
This salt, out of a strong solution, also frequently crystallizes 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 filtration or crystallization. Analyses of this altered 
salt are given, page 504. 
The salt crystallized in the air-pump lost water in water-bath. 
20‘415grs. lost at 212° 3'1'lOgrs. 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 sulphuric 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*240 grs. gave 10*198 grs. sulphate of barytes and 3*480 grs. oxide of iron. 
The combustions were made with chromate of lead. 
I. 8*539 grs. gave 1*208 gr. water and 4*665 grs. carbonic acid. 
II, 10*068 grs. gave 1*132 gr, water and 5*580 grs. carbonic acid. 
I. 
II. 
Calculated. 
Iron . . 
14*073 
14*129 
5 
140 
14*05 
Barium . 
34*446 
34*791 
5 
343 
34*43 
Carbon , 
14*899 
15*075 
24 
144 
14*45 
Hydrogen 
1*571 
1*249 
15 
15 
1*50 
Nitrogen ' 
j- 35*011 
34*756 
15 
2101 
35*57 
Oxygen J 
18 
144 J 
100*00 
100*00 
996 
100*00 
