290 On the Chemical Formula of the Nitroprussides. 



regard it as the expression of the analytical results. I selected 

 for this purpose the soda salt, which is the most easily crystal- 

 lized. The impure nitroprusside of sodium, which was ob- 

 tained in solution by the saturation of the acid with carbonate 

 of soda, was precipitated by the addition of sulphate of copper 

 in the form of nitroprusside of copper ; this was thoroughly 

 washed with water, and lastly carefully decomposed by caustic 

 soda. The solution of nitroprusside of sodium thus obtained 

 was separated by filtration from the oxide of copper liberated, 

 and evaporated at a gentle heat ; large crystals were then ob- 

 tained, which I submitted to analysis. 



The iron and soda were estimated in the form of peroxide 

 of iron and sulphate of soda, after the decomposition of the 

 salt with concentrated sulphuric acid. 



I. 0*531 grm. gave 0*1490 grm. of peroxide of iron and 

 0*2505 grm. of sulphate of soda. 



II. 0*471 grm. gave 0*1330 grm. of peroxide of iron and 

 0*2223 grm. of sulphate of soda. 



Regarding the combustions, the first was made with chro- 

 mate of lead, the second with peroxide of copper and oxygen 

 gas. 



I. 0-5157 grm. gave 0*3937 grm. of carbonic acid and 0*0610 

 grm. of water. 



II. 0'4394 grm. gave 0*3265 grm. of carbonic acid and 

 0*0526 grm. of water. 



The determination of the nitrogen was made according to 

 the method of Dumas : 0298 grm. gave 74 cub. cent, of moist 

 nitrogen at 57° F., and with the barometer at 28". 



I shall now compare these results with those of the com- 

 position calculated according to the simplest formula given by 

 Playfair, and the mean of the same chemist's analyses of the 

 soda salt obtained by the same method. 











Found. 





Mean of 











A 





Playfair's 

 analyses. 





Eq. 



Calc. 



I. 



II. 



Mean. 



Iron . . 



2 



19*48 



19-64 



19-77 



19*70 



19-33 



Sodium . 



2 



15*9S 



15-41 



15*42 



15-42 



15-48 



Carbon . 



10 



20*66 



20*82 



20-26 



20-54 



20-17 



Hydrogen 



4 



1-38 



1-31 



1-33 



1-32 



1-53 



Nitrogen 



6 



28-93 



29-35 



• •• 



29-35 



27-78 



Oxygen . 



5 



13-77 



... 



• »• 



13-66 





100-00 100-00 



Playfair's more complicated formula, Fe 5 Cy 12 , 3 NO, 5Na 



+ 10HO, requires in 100 parts, 19*33 Fe, 16*02 Na, 19*89 C, 



1-38 H, and 29*00 N. It is evident, therefore, that in regard 



to the amount of soda and carbon, the analysis corresponds 



