Chemical and Physical Papers. 87 



Found. Calculated. 



NH 9.62 9.49 



K 5.10 5.15 



Ca 13.18 13.19 



Fe 18.48 18.39 



H2O 2.24 2.37 



When potassium ferrocyanide is added to a barium salt under 

 similar conditions, a light yellow, heavy, granular precipitate falls, 

 which is soluble enough in hot water so as to admit of crystalliza- 

 tion from that solvent. This fact was known to Thenard, since he 

 suggests the separation of barium from strontium by precipitating 

 the barium in ammonia solution by means of potassium chromate, 

 (Children's translation of Thenard's Essey on Chemical Analysis, 

 1819, p. 123). The analysis of the material, air-dried on a porous 

 plate, gave results corresponding to the formula K2BaFe (CN)6, 

 4(NH4)BaFe(CN)6l5H20. 



Found. Calculated. 



K 8.55 3.49 



NH4 6.76 6.44 



Ba 30.46 30.67 



Fe 12.53 12.48 



H2O 11.80 12.06 



Magnesium salts under these same conditions give a fine white 

 precipitate, difficultly soluble in water and acids. In Watts's Dic- 

 tionary, edition of 1869, a ferrocyanide of magnesium and am- 

 monium is mentioned as having been obtained, but in an impure 

 state. The cause of this lies in the carrying down of a slight ex- 

 cess of magnesium, probably due to the formation of a small 

 amount of Mg2Fe(CN)6. The product carefully washed and air- 

 dried to constant weight gave figures which correspond best to this 

 formula: K2MgFe(CN)6, 5(NH4)MgFe(CN)6lOH20. 



Found. Calculated. 



Ka 3.85 4.22 



NH4 9.79 9.72 



Mg 8.43 7.87 



Fe 17.96 18.06 



H2O 9.94 9.70 



