502 
DR. PLAYFAIR ON THE NITROPRUSSIDES, 
I. 4*494 grs. salt gave 112 C.C. gas, the therm, being 47°^ Fahr., barom. 29*844 in. 
II. 3*372 grs. salt gave 83 C.C. gas, the therm, being 50° Fahr., barom. 29*550 in. 
This, calculated on 22*7 per cent, carbon, gives 43*619 per cent, nitrogen. 
Again, 8*747 grs. salt distilled with a weak solution of soda, gave a distillate which, 
collected in hydrochloric acid, yielded 15*021 grs. platinum salt. 
Iron . . . 
I. 
. 22*177 
II. 
21*993 
III. 
Mean. 
22*085 
Carbon . . 
. 22*901 
22*420 
22*755 
22*692 
Hydrogen 
. 3*283 
3*204 
3*095 
3*194 
Nitrogen . . 
. 46*894 
45*076 
.... 
45*985 
Oxygen . . 
4*745 
7*307 
.... 
6*044 
100*000 
100*000 
100*000 
The ammonium per cent, from the amount of platinum salt is 13*872. 
It is obvious that there is little hydrogen as water, for the greatest part is required 
to make up the ammonium (13*872 per cent, requires 3*08 hydrogen). Reserving, 
as in the other cases, the discussion as to the cause of difference between this salt 
and the pure nitroprusside, it will be convenient to give the calculation for nitro- 
prusside of ammonium, of which the formula would be Fe 5 Cyi 2 3NO, 5 NH 4 + 2 HO. 
5 Iron . . . 
... 140 
22*36 
24 Carbon . . 
... 144 
23*00 
20 Nitrogen . 
... 280 
44*72 
22 Hydrogen , 
... 22 
3*51 
5 Oxygen . . 
... 40 
6*41 
626 
100*00 
The hydrogen, but not the other constituents, would agree better with the above 
formula minus 2 equivs. of water ; the hydrogen by the latter would be 3*28 per cent. 
Nitroprusside of Calcium. 
21 . To prepare this salt, nitroprusside of iron or of copper is decomposed by miJk 
of lime, the nitroprusside being kept in decided excess. A dark red solution is ob- 
tained, which on evaporation, even at a gentle heat, deposits prussian blue. When 
sufficiently concentrated the solution yields crystals of a dark red colour, and of 
considerable lustre. The crystals belong to the oblique system. They have been 
approximatively measured by Prof. Miller. 
Symbols : — a 100 , c 001 , m 1 10 ; there are besides one or two faces 
in the zone c m c', the symbols of which have not been found. 
Cleavage a very perfect. 
Angles between normals to faces approximately : — 
17L' 
ac 82 0 
ma 70 0 
mm' 40 0 
