496 
DR. PLAYFAIR ON THE NITROPRUSSIDES, 
Corrected vol. of mixed gases . . . 123‘180 
Corrected vol. of nitrogen .... 47*491 
Corrected vol. of carbonic acid . . 75’689 
Hence the proportion of nitrogen to carbonic acid is 1 ; 1*593, which calculated on 
the mean quantity of carbon (21*25), yields 31*12 per cent, nitrogen. 
III. Liebig’s method : — 
Tubes. Vol. mixed gases. 
Vol. after absorption. 
Vol. of carbonic acid. 
1. 
21-2 
8-0 
13-2 
2. 
22-4 
9-1 
13-3 
3. 
26-0 
10-4 
15-6 
4. 
21-7 
8-2 
13-5 
5. 
28-3 
10-6 
17*7 
6. 
17*9 
6*7 
11-2 
7. 
22-2 
8-2 
14-0 
8. 
19-8 
* 7*5 
12-3 
9. 
20-0 
8-0 
12-0 
10. 
22-7 
9-0 
13-7 
11. 
28-0 
10-8 
17*2 
12. 
19-2 
7*3 
11-9 
13. 
14-6 
5-4 
9-2 
284-0 
109-2 
174-8 
Hence the proportion of nitrogen to carbonic acid 
is 1 : 1-60. 
I. 
II. 
III. IV. 
Mean. 
Calculated. 
Iron . . . 
20-506 
20-400 
.... .... 
20-453 
5 
140 
20-43 
Copper . . 
22-708 
22-880 
.... .... 
22-794 
5 
158 
23-06 
Carbon . . 
21-351 
21-255 
21-222 21-179 
21-251 
24 
144 
21-02 
Hydrogen . 
0-315 
0-309 
0*371 0-308 
0-325 
1 
1 
0-14 
Nitrogen . 
29-856 
31-120 
30-980 .... 
30-652 
15 
210 
30-65 
Oxygen . . 
5-264 
4-036 

4-515 
4 
32 
4-70 
100-000 
100-000 
100-000 
685 
100-00 
The formula of the copper salt is therefore Fe 5 Cyi 2 
3NO, CU5 + HO. 
Nitroprusside of Iron. 
16. This salt is obtained by adding sulphate of the protoxide of iron to a soluble 
nitroprusside. When the solutions are dilute the precipitate does not at first appear ; 
as however it is very sparingly soluble, it may be purified by washing either with hot 
or cold water. 
This salt is a salmon-coloured precipitate, nearly though not absolutely insoluble 
in water ; it is more soluble in water rendered acid by nitric acid. It is decomposed 
by caustic alkalies, with the precipitation of oxide of iron and the formation of a 
