AMMONIA-COBALT BASES. 53 



The analysis was made in this case by gently igniting the salt in a platinum 

 crucible, and afterwards dissolving out the chloride of cobalt by long boiling with 

 chlorhydric acid. 



CELORHYDRARGYRATE op xanthocobalt. 



This salt is formed by adding a cold solution of chloride of mercury to a solution 

 of the chloride of Xanthocobalt. It is usually thrown down in the form of brilliant 

 pale brownish-yellow talcose scales, which on re-solution in hot water containing 

 a little free chlorhydric acid, separate as the solution cools in brown-yellow 

 needles. The two forms appear to have the same chemical constitution. The salt 

 is quite insoluble in cold, and with difficulty soluble in hot water, but the solution 

 occurs without sensible decomposition. The chlorhydrargyrate of Xanthocobalt 

 has the formula 



N0 2 .5NH 3 .Co 2 0,ci 2 +4HgCl+2HO. 



as the analyses satisfactorily show : 



0.1025 grs. gave 0.1315 grs. sulphate of cobalt = 1.44 per cent, cobalt. 

 0.8898 grs. gave 0.9311 grs. chloride of silver = 26.05 per cent, chlorine. 



The formula requires 





Eqs. 



Calculated. 



Found. 



Cobalt 



. 2 



1.25 



1.44 



Chlorine 



. 6 



26.19 



26.05 



FERROCYANIDE OF XANTHOCOBALT. 



This salt is precipitated almost immediately when a solution of ferrocyanide 

 of potassium is added to one of the nitrate of Xanthocobalt. We have not been 

 able to obtain it, however, either from the chloride or the sulphate, with which the 

 ferrocyanide of potassium gives only turbid solutions. The salt is precipitated in 

 prismatic crystals which appear to belong to the oblique rhombic system. Its color 

 is a very beautiful bright orange-reel, corresponding nearly with the red-orange No. 

 5, of the 2d circle of Chevreul's scale. When freshly prepared, it is one of the 

 most beautiful salts which chemistry can exhibit, but it loses some of its brilliancy 

 of tint by keeping, and becomes a little duller and darker, probably from a slight 

 decomposition upon the surface. The crystals exhibit a fine dichroism by reflection, 

 the ordinary image being pale reddish orange, while the extraordinary image is 

 bright orange. The ferrocyanide of Xanthocobalt is almost insoluble in cold, and is 

 immediately decomposed by hot or even by warm water. The crystals lose water 

 and are partially decomposed in vacuo, or even in pleno over sulphuric acid. They 

 can, therefore, only be dried by pressure between folds of bibulous paper. The 

 impossibility of purifying this salt by recrystallization, and the facility with which 

 it is decomposed, render it difficult to obtain it in a perfectly pure state. 



