a New Class of Salts. 349 



pressed between folds of bibulous paper and dried in vacuo 

 over sulphuric acid. It may be called nitroprusside of 

 potassium and potash. 



This salt is of a bright yellow colour and of crystalline ap- 

 pearance. 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 

 chromate of lead. Salts of iron are precipitated of a yellowish- 

 brown, and salts of copper of a brown colour. On the addi- 

 tion of an acid, the excess of potash is removed and nitro- 

 prusside of potassium remains in solution ; the salt therefore 

 is a compound of a nitroprusside with potash. It will not 

 crystallize m vacuo, its solution decomposing with the depo- 

 sition of an oxide of iron, and with the escape of a gas which 

 communicates 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 ana- 

 lyses therefore give only approximative results; they were 

 made in the usual way by decomposing the salt with fuming 

 sulphuric acid. 



I. 17-350 grs. gave 3-4.40 grs. Fe^O^and 14-32 KO, SO^. 



II. 37-870 grs. gave 7*345 grs. Ye^ O^and 30-53 KO, 80^. 

 The combustions were made with chromate of lead. 



I. 14-075 grs. gave 7*765 grs. CO^ and 1-015 gr. HO. 



II. 13-71 grs. gave 7*490 grs. CO^ and 0-985 gr. HO. 

 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 3614 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 j 3^.^^ 33.^^ ri5 210| 33.^^ 



Oxygen J 1^15 120 J 



10000 100*00 100*00 973 100*00 



Hence this salt differs from nitroprusside of potassium by 

 containing 4 atoms of potash attached. Its formula is there- 

 fore tV Cy'2 3NO, K^ + 4KO + 8HO. There is little doubt 



