A NEW CLASS OF SALTS. 
509 
The salt is now pressed between folds of bibulous paper and dried in vacuo over sul- 
phuric acid. It may be called nitroprusside of potassium and potash. 
This salt is of a bright yellow colour and of crystalline appearance. It is very 
sparingly soluble in alcohol, but very soluble in water, to which it gives a strong 
alkaline reaction. It precipitates salts of lead of a fine yellow colour like the chro- 
mate of lead. Salts of iron are precipitated of a yellowish brown, and salts of copper 
of a brown colour. On the addition of an acid, the excess of potash is removed and 
nitroprusside of potassium remains in solution ; the salt therefore is a compound of a 
nitroprusside with potash. It will not crystallize in vacuo, its solution decomposing 
with the deposition of an oxide of iron, and with the escape of a gas which commu- 
nicates a pink colour to the sulphuric acid used for the evaporation in the air-pump. 
The salt heated in a tube evolves nitric oxide and ammonia, and leaves a black residue 
which yields to water an alkaline solution of a nitroprusside. When its solution in 
water is boiled, complete decomposition takes place, a ferrocyanide, oxide of iron, 
nitrite and oxalate of potash being produced. 
It is almost impossible to obtain it free from uncombined nitroprusside, which is 
observed to remain in solution when a salt of lead is added to it. If potash in excess 
be used, it is equally difficult to remove the excess by washing. The analyses there- 
fore give only approximative results ; they were made in the usual way by decomposing 
the salt with fuming sulphuric acid. 
I. 17*350 grs. gave 3'440grs. peroxide of iron and 14'32 grs. sulphate of potash. 
II. 37*870 grs. gave 7*345 grs. peroxide of iron and 30*53 grs. sulphate of potash. 
The combustions were made with chromate of lead. 
I. 14’075 grs. gave 7*765 grs. carbonic acid and TO 15 gr. water. 
II. 13*71 grs. gave 7*490 grs. carbonic acid and 0*985 gr. water. 
The samples of salt analysed were made at different times. 
I. 
II. 
Mean. 
Calculated. 
Iron .... 
13*87 
13*57 
13*72 
5 
140 
14*38 
Potassium . . 
37*00 
36*14 
36*57 
9 
351 
36*07 
Carbon . . 
15*04 
14*89 
14*96 
24 
144 
14*79 
Hydrogen 
0*80 
0*79 
0*79 
8 
8 
0*82 
Nitrogen "l 
Oxygen / ’ 
33*29 
34*61 
33*96 
rl5 
1 15 
210-) 
120 J 
33*94 
100*00 
100*00 
] 00*00 
973 
100*00 
Hence this salt differs from nitroprusside of potassium by containing 4 atoms of 
potash attached. Its formula is therefore Peg Cy^g 3NO K5-l-4KO-}-8HO. There is 
little doubt that it might, when quite free from nitroprusside, contain an additional 
equivalent of potash. 
It has been stated that a solution of this salt is decomposed on boiling. Oxide of 
iron falls down, nitrogen escapes, and the solution is now found to contain ferro- 
cyanide of potassium, nitrite of potash and traces of oxalate of potash. 
3 u 
MDCCCXLIX. 
