AMMONIA-COBALT BASES. 35 



LUTEOCOBALT. 



The salts of Luteocobalt have a yellow or brown-yellow color, and are almost 

 always well crystallized. They are in general more soluble in water than the 

 corresponding salts of Roseocobalt; the solutions have a brown-yellow color. The 

 salts of Luteocobalt are very stable in the presence of acids in general, but are 

 decomposed by long heating with sulphuric acid. The neutral and alkaline solu- 

 tions are readily decomposed by boiling, like the salts of the other cobalt bases. 

 Nearly all of them have a purely saline taste. When hydrated, these salts gene- 

 rally effloresce in dry air or in vacuo, and become opaque, with a peculiar porce- 

 lain-like lustre and reddish-buff color. The salts of Luteocobalt may be formed, 

 like those of the other bases described, by direct oxidation : it is well worthy of 

 notice, however, that they are often found among the products of the decomposition 

 of the salts of Roseocobalt and Purpureocobalt. This is especially remarkable, 

 because the constitution of Roseocobalt is simpler than that of Luteocobalt, the 

 former base being 5NH 3 .Co 2 3 , while the latter is 6NH 3 .Co 2 3 . We have here a 

 singular inversion of the usual law, that the products of the decomposition of a 

 complex molecule are more simple in constitution than the body decomposed. 



Luteocobalt, like Roseocobalt, is a triacid base. 



CHLORIDE OF LUTEOCOBALT. 



When an ammoniacal solution of chloride of cobalt, to which a large quantity of 

 coarsely powdered chloride of ammonium has been added, is exposed to the air for 

 some days, it often happens that no traces of chloride of Roseocobalt or Purpureocobalt 

 are found, but the bottom of the vessel becomes covered with orange-yellow crys- 

 tals, which are the chloride of Luteocobalt. Chlorhydric acid precipitates an addi- 

 tional quantity of the salt from the supernatant liquid. The raw chloride, as thus 

 obtained, is easily purified by solution in hot water, filtration, and repeated crys- 

 tallization. This method of preparing the salt is by no means always successful, 

 and very frequently results only in the formation of chloride of Roseocobalt and 

 Purpureocobalt, with scarcely a trace of the chloride of Luteocobalt. We have, 

 however, almost invariably succeeded in preparing, by this process, a mixture of 

 the sulphate and chloride of Luteocobalt, by employing a solution containing both 

 the chloride and sulphate of cobalt. The sulphato-chloride resulting, by boiling 

 with chlorhydric acid and chloride of barium, yields a solution from which the pure 

 chloride may be obtained by repeated crystallization. The chloride of Luteocobalt 

 crystallizes by slow evaporation, in remarkably beautiful brownish-orange colored 

 crystals, which belong to the trimetric or right rhombic system, and which are 

 isomorphous with the sulphate of Luteocobalt. According to Prof. Dana, the usual 

 forms are, in his modification of Naumann's notation, 0, 00, t, co-T , 1 - 00, s - 60, 



