500 
DR. PLAYFAIR ON THE NITROPRUSSIDES, 
The combustions were made in the usual way. 
I. 7’720 gi'S. gave 7’005 grs. carbonic acid and I *175 gr. water. 
II. lO'SlO grs. gave 9*880 grs. carbonic acid and T665 gr. water. 
III. 4*385 grs. gave 3*980 grs. carbonic acid and 0*700 gr. water. 
An estimation of nitrogen by Bunsen’s method gave the following result : — 
Obs. vol. 
Barom. 
inches. 
Therm. 
Col. Merc. 
Vol. of mixed gases (moist) . 
. 89*5 
29*994 
foe. 
152*7 
Vol. after absorption (dry) . 
. 37-4 
30*015 
9*2 C. 
205*2 
Corrected vol. of mixed gases , . . 52*995 
After absorption of carbonic acid . . 20*570 
Nitrogen 32*425 
Hence the proportion of nitrogen to carbonic acid is 1 : 1*576. 
Iron .... 
I. 
. 23*88 
II. 
23*69 
III. 
23*85 
Mean. 
23*80 
5 
140 
Calculated 
24*26 
Carbon . . 
. 24*74 
24*92 
24*75 
24*80 
24 
144 
24*95 
Hydrogen . 
. 1*69 
1*71 
1*77 
1*72 
11 
11 
1*90 
Nitrogen . . 
. 36*73 
36*73 
36*73 
36*73 
15 
210 
36*39 
Oxygen . . 
. 12*96 
12*95 
12*90 
12*95 
9 
72 
12*50 
100*00 
100*00 
100*00 
100*00 
577 
100*00 
The calculated result, especially as regards the hydrogen, is not sufficiently close to 
be the true expression of the analysis, but it is here given to show how far the acid 
differs from pure nitroprussic acid. It is indeed probable that the acid dried at 212° 
only contains 10 equivs. of water. 
The acid is so remarkably deliquescent that it is very difficult to ascertain how 
much the crystals lose in the water-bath. The following analysis of the salt dried 
in vacuo over sulphuric acid shows a higher state of hydration. The sample analysed 
had never been heated, even in solution, so that it evaporated without the deposition 
of oxide of iron. Still the oxide was detected in the mother-liquor by ferrocyanide 
of potassium. 
I. 3*225 grs. gave TO 10 gr. peroxide of iron. 
II. 3*235 grs. gave 1*020 gr. peroxide of iron. 
I. 5*830 grs. gave 5*020 grs. carbonic acid and 1*09 gr. water. 
II. 8*225 grs. gave 7'060 grs. carbonic acid and 1*51 gr. water. 
I. 
II. 
Mean. 
Iron . . 
. . . 21*92 
22*07 
21*99 
Carbon 
. . . 23*48 
23*32 
23*40 
Hydrogen 
. . . 2*07 
2*03 
2*05 
Nitrogen . 
Oxygen . 
■ ■ '1 52*53 
52*58 
52*56 
100*00 
100*00 
100*00 
