48 RESEARCHES ON THE 



OXIDE OF LtTTEOCOBALT. 



The oxide of Luteocobalt may be obtained by decomposing a solution of the 

 sulphate with baryta water. The solution is brown-yellow, and has an alkaline 

 taste and reaction. It cannot be evaporated without decomposition, ammonia being 

 evolved and a black powder separated. The solution absorbs carbonic acid from 

 the air, and on evaporation, yields crystals of the carbonates; with acids it yields 

 the salts of the base. The oxide of Luteocobalt appears to form compounds with 

 salts of copper, which may be analogous to the ammonia-salts of that metal, or 

 which again may be only double salts of copper and Luteocobalt. A solution of 

 the oxide added to one of sulphate of copper gives, after standing, beautiful chrome- 

 green crystals of a new salt, which we have not yet had an opportunity of examining. 



XANTHOCOBALT. 



The salts of Xanthocobalt may be prepared by two distinct processes, either 

 directly from ammoniacal solutions of salts of cobalt, or from neutral, acid, or 

 ammoniacal solutions of the salts of Roseocobalt or Purpureocobalt. In any case, 

 the gas arising from the action of nitric acid upon starch or sawdust, and which 

 may be considered as a mixture of C0 2 , N0 2 , N0 3 , and N0 4 — the last probably in 

 excess — is to be passed into the solution. A more or less rapid absorption accom- 

 panied by copious fumes of carbonate of ammonia takes place. The color of the 

 liquid gradually changes to a dark reddish-brown or dark sherry-wine color, and 

 the liquid on cooling generally deposits an abundance of a salt of Xanthocobalt in 

 brown-yellow crystals. When a current of the red gas above mentioned, and 

 which we shall denote by the symbol NO x , is passed into an acid solution of cobalt 

 and ammonia, an absorption also usually takes place, but in this case no Xantho- 

 cobalt is produced, but only a beautiful yellow crystalline salt, which is the ammo- 

 nia nitrite of cobalt, corresponding to the yellow potash salt, first described by 

 Fischer, 1 some years afterward re-discovered and analyzed by St. Evre, 2 and finally 

 examined by Stromeyer. 3 The formation of this compound is easily prevented by 

 keeping the solution ammoniacal by constant additions of ammonia. 4 



1 Pogg. Ann., LXXIV, 115, and LXXXVIII, 496. 



s Compt. Rend., XXXIV, 479, and Ann. de Chimie et de Physique, XXXVIII, ITT. 



8 Journ. fur Pract. Chemie, LXI, 41, and Annalen der Chemie und Pharmacie, XCVI, 218. 



4 The employment of the double nitrite of cobalt and potash as a means of separating cobalt from 

 other metals was first suggested by Fischer, and afterward by St. Evre and Stromeyer. As the salt 

 is insoluble in a solution of acetate of potash and in alcohol, it is easy to wash it completely, but after 

 washing it is difficult to estimate the cobalt accurately by drying and weighing upon a filter. We 

 have found that a very satisfactory result may be obtained by weighing the cobalt in the form of mixed 

 sulphates of cobalt and potash. According to Stromeyer, Fischer's salt has the formula 



Co a O a -2N0 3 +3KO,N0 3 + 2HO. 



