a New Class of Salts. 351 



manner. A weighed quantity of a nitroprusside was dissolved 

 in water and boiled, caustic potash or caustic soda (according 

 as the nitroprusside was a salt of potassium or sodium) being 

 added to the boiling solution, until a drop taken out gave, 

 after being neutralized, no purple colour with a sulphide. 

 The precipitated oxide of iron was now collected and weighed. 

 The filtrate was precipitated by alcohol, and the prusside 

 collected and determined on a weighed filter. The filtrate 

 was now neutralized with acetic acid, and chloride of calcium 

 added, but the oxalate of lime was generally not in sufficient 

 quantity to collect and weigh, mere traces being obtained. It 

 was now attempted to estimate the amount of nitrate by the 

 process described by Nesbit for analysing nitrates*, that is, 

 by converting its nitrogen into ammonia by zinc and muriatic 

 acid, the hydrogen being slowly evolved. The ammonia thus 

 formed was separated by distillation with caustic soda, col- 

 lected in muriatic acid and determined as chloride of platinum 

 and ammonia. This process did not however give constant 

 results in my hands, probably from the difficulty of preventing 

 the escape of nitric oxide on adding an acid to the nitrite. 

 The nitrite was therefore determined by loss. In one case 

 only did I, by the above process, obtain a result approaching 

 the quantity of nitrite in solution. 



17*24 grs. of nitroprusside of sodium were dissolved in 

 water, the solution was boiled and caustic soda added, keeping 

 the solution distinctly alkaline after ebullition had continued 

 for some time. It yielded 0*92 gr. peroxide of iron, and 

 I'l'-SS grs. ferrocyanide of sodium; the residual liquid, treated 

 according to Nesbit's plan, only gave 2'57 grs. platinum salt. 



Iron precipitated . . . 3*73 per cent. 

 Iron in prusside . . . 15*08 per cent. 



18'81 



Hence all the iron, except about 0*5 per cent., is found in 

 the oxide of iron and in the prusside ; the remainder is pro- 

 bably in the minute quantity of pink salt alluded to above. 

 The carbon contained in the prusside amounts to 20*3 ; so 

 that the total quantity of cyanogen has gone down in that 

 form, the carbon in the nitroprusside being 20*0 per cent. 



It will be seen that the iron precipitated as peroxide of iron 

 is one-fourth that retained in the ferrocyanide. The following 

 equation expresses the transformation : — 



2(Fe^Cyi2 3NO, Na^) + 9NaO = 4(Fe2Cy6,Na4)-}-3NaO,N03 

 + Fe2 03-H3N. 



* Memoirs of Chemical Society. 



