AMMONIA-COBALT BASES. 39 



CHLORAURATE OP LUTEOCOBALT. 



A solution of terchloride of gold produces immediately in solutions of the chloride 

 of Luteocobalt a beautiful yellow precipitate of small granular crystals. These 

 crystals are very insoluble in cold water, but more readily soluble in boiling water 

 acidulated with chlorhydric acid. Reducing agents separate gold with full metallic 

 lustre. The formula of this salt is 



6NH 3 .Co 2 Cl 3 +AuCl 3 



as the analyses satisfactorily show : 



^ 0.7308 grs. gave 0.1025 grs. Co 6 7 = 10.53 per cent, cobalt. 



0.7308 grs. gave 0.2530 grs. gold = 34.62 per cent. 



0.6451 grs. gave 0.9714 grs. chloride of silver = 37.36 per cent of chlorine. 



Eqs. Calculated. Found. 



Cobalt ... 2 10.33 10.53 



Gold ... 1 34.50 34.62 



Chlorine ... 6 37.30 37.36 



IODIDE OF LUTEOCOBALT. 



Iodide of potassium produces immediately in solutions of the chloride, sulphate, 

 or nitrate of Luteocobalt, a remarkably beautiful bright yellow precipitate of the 

 iodide of Luteocobalt. This precipitate is rather insoluble in cold water, but 

 readily soluble in hot water. The solution yields by spontaneous evaporation 

 brown-yellow crystals, which appear to have the same form as the chloride. 



0.2224 grs. of this salt gave 0.06308 grs. sulphate of cobalt, corresponding to 10.79 per cent, cobalt. 



The formula 6NH 3 .Co 2 T 3 requires 10.88 per cent, cobalt. 



The color of the precipitated and dried iodide is very fine, and its brilliancy 

 led us to hope that it might be advantageously employed as a pigment. On trial, 

 however, the color was found wanting in body ; the yellow, moreover, changes to 

 a brown-yellow when the powder is ground in oil or water. 



BROMIDE OF LUTEOCOBALT. 



Bromide of potassium gives a rather dull yellow precipitate in solutions of 

 Luteocobalt. The precipitate, re-dissolved in hot water, gives, on slow evapora- 

 tion, wine-yellow crystals of the bromide. These crystals have the same form as 

 those of the chloride, and their formula is therefore 



6NH,.Co 2 Br 3 . 



