276 Dr. Playfair oti the Ntiroprussides, 



The nitrogen was determined by Dumas' quantitative me- 

 thod. 



I. 4*494 grs. salt gave 112 C.C. gas, the therm, being 

 47°^ Fahr., barom. 29-844 in. 



II. 3*372 grs. salt gave 83 C.C. gas, the therm, being 

 50° Fahr., barom. 29*550 in. 



This, calculated on 22*7 per cent, carbon, gives 43-619 

 per cent, nitrogen. 



Again, 8747 grs. salt distilled with a weak solution of soda, 

 gave a distillate which, collected in hydrochloric acid, yielded 

 15*021 grs. platinum salt. 



The ammonium per cent, from the amount of platinum salt 

 is 13*872. 



It is obvious that there is little hydrogen as water, for the 

 greatest part is required to make up the ammonium (13*872 

 per cent, requires 3*08 hydrogen). Reserving, as in the other 

 cases, the discussion as to the cause of difference between this 

 salt and the prue nitroprusside, it will be convenient to give 

 the calculation for nitroprusside of ammonium, of which the 

 formula would be Fe^Cy^^sNO, 5NH4-f-2HO. 



626 100-00 



The hydrogen, but not the other constituents, would agree 

 better with the above formula minus 2 equivs. of water; the 

 hydrogen by the latter would be 3*28 per cent. 



Nitroprusside of Calcium. 



21. To prepare this salt, nitroprusside of iron or of copper 

 is decomposed by milk of lime, the nitroprusside being kept 

 in decided excess. A dark red solution is obtained, which 

 on evaporation, even at a gentle heat, deposits prussian blue. 

 When sufficiently concentrated the solution yields crystals 

 of a dark red colour, and of considerable lustre. The crystals 



