512 
DR. PLAYFAIR ON THE NITROPRUSSIDES, 
however be obtained in a solid state when alcoholic solutions of the two salts are 
employed. In order to obtain it in this state, nitroprusside of sodium is dissolved in 
the smallest possible quantity of water, and to this solution is added four or five times 
its bulk of alcohol. An alcoholic solution of neutral sulphide of sodium (the sulphide 
obtained by reducing- the sulphate with hydrogen) is now added to the alcoholic 
solution of nitroprusside, the addition being stopped before the supernatant liquid 
gives a decidedly black reaction on lead paper. The mixed solutions acquire a 
magnificent purple blue colour. On stirring the mixture, an aqueous solution of the 
purple compound falls down in oily drops. After this has settled, the alcohol is de- 
canted, and the blue solution is washed repeatedly and quickly with alcohol by de- 
cantation. It is now, as rapidly as possible, put in vacuo over sulphuric acid, when 
it soon parts with its water and becomes solid. It usually dries to a dirty green 
powder, which is a mixture of the purple compound with the products of its decom- 
position. It may however, though this is rare, dry quite unchanged in its character, 
being still of a fine blue colour and dissolving entirely in water with all its magnifi- 
cent purple blue shade. It cannot then be dried in the water-bath, where it quickly 
decomposes and becomes green. 
The following analysis was made on two portions which were dried in the air-pump, 
until they ceased to lose weight and had all their properties unchanged. They were 
oxidized by nitrate of ammonia; the residue was dissolved in nitric acid. The iron 
was precipitated as peroxide, the sulphur estimated as sulphate of barytes, and the 
soda as a sulphate. 
I. 14’210grs. gave 3‘420 grs. peroxide of iron, 5’710grs. sulphate of barytes and 
9'38 grs. sulphate of soda. 
II. 8’99 grs. gave 3*88 grs. sulphate of barytes and 6*62 grs. sulphate of soda, the iron 
being aceidentally lost. 
The combustion was made by chromate of lead, peroxide of lead being used to 
arrest the sulphurous acid. 
I. 6‘20 grs. gave 3-855 grs. carbonic acid and 0-440 gr. water. 
II. 10-565 grs. gave 6-810 grs. carbonic acid and 0-675 gr. water. 
I. 
II. 
Mean. 
Iron . . . 
. . 16-84 
16-84 
16-84* 
Sodium . . 
. . 21-37 
23-84 
22-60 
Sulphur . . 
. . 5-51 
5-92 
5-71 
Carbon . . 
. . 16-95 
17-58 
17-27 
Hydrogen . 
Nitrogen ) 
. . 0-78 
0-71 
0-74 
Oxygen J ’ 
. . 38-55 
35-1 1 
36-84 
100-00 
100-00 
100-00 
* It should be stated that in many analyses of this compound in its partially decomposed state, the most 
discordant results were obtained. The two analyses here adduced were made on the only specimens which 
appeared to be unchanged ; in all the other cases the compound had become green and therefore was decom- 
posed, as it no longer dissolved in water with its characteristic purple tint. 
