44 RESEARCHES ON THE 



Our formula requires 





Bqs. 





Calculated. 



Mean. 





Found. 



Cobalt . 



2 



59.0 



16.85 



16.83 



16.80 



16.85 



Sulph. acid 



. 3 



120.0 



34.28 



34.42 



34.52 



34.32 



Hydrogen 



. 23 



23.0 



6.5? 



6.69 



6.U 



6.6? 



Nitrogen 



. 6 



84.0 



24.00 



23.97 



24.00 



23.85 



Osygen . 



. 8 



64.0 



18.28 



18.09 



— 



— 



16.83 



350.0 100.00 



According to Fremy, the sulphate contains but four equivalents of water of 

 crystallization. In vacuo or in dry air the sulphate of Luteocobalt effloresces, 

 becomes opaque and reddish buff colored, and loses 4 eqs. or 10.13 per cent, of 

 water. 



Rogojski did not succeed in obtaining the sulphate of Luteocobalt by decomposing 

 the chloride with sulphate of silver. According to this chemist, there is produced 

 under these circumstances a sulphato-chloride which has the formula 



6NH s .Co a 8 ,3SOj+ 6NH 3 .Co 2 Cl 3 . 



"We have already mentioned, however, that the chloride and sulphate of Luteo- 

 cobalt are isomorphous, and we have accordingly found, as might be expected, that 

 these two salts are capable of crystallizing together in all proportions, and cannot 

 be separated by crystallization alone. To show the variation in the constitution 

 of the mixed chloride and sulphate, it will be sufficient to give a few cobalt deter- 

 minations made with the salt as prepared at different times. 



0.1510 grs. gave 0.0673 grs. sulphate of cobalt = 16.96 per cent, cobalt. 

 0.7075 grs. " 0.3210 grs. " " = 17.26 



0.1205 grs. " 0.0680 grs. " " = 21.47 



The parallel which Rogojski draws between the salt which he analyzed and the 

 sulphate of Gros's base, which Gerhardt considers as a sulphato-chloride of Dipla- 

 tinamin, must therefore be considered as illusory. 



CHROMATE OF LUTEOCOBALT. 



A solution of the neutral chromate of potash gives a fine yellow precipitate in 

 solutions of the chloride, nitrate, and sulphate of Luteocobalt. The precipitate is 

 soluble in hot water, and crystallizes readily from the solution in brown-yellow 

 crystals, which resemble those of the sulphate. We have not analyzed this salt, 

 but it is almost certain that its true formula is 



6NH 3 .Co 2 3 ,3Cr0 3 +5HO, 



since it forms with chloride of Luteocobalt crystallizable mixtures in various pro- 

 portions, which exhibit in the greatest beauty and distinctness the characteristic 

 forms of the crystals of the sulphato-chlorides above alluded to. The pure chromate 

 can only be obtained by precipitating the nitrate of Luteocobalt by chromate of 

 potash, as the precipitate from the chloride always contains chlorine, and that from 

 the sulphate, sulphuric acid. 



