

AMMONIA-COBALT BASES. 7 



boiling it with a little ammonia. After complete precipitation of the sesquioxide 

 of cobalt, chlorhydric acid is to be added to reduce and dissolve the oxide, when 

 the sulphuric acid may be directly thrown down by chloride of barium. Even 

 with these precautions, our results are not unfrequently two-tenths or three-tenths 

 of one per cent, too high, almost never too low. 



Oxalic Acid. The ordinary methods for the quantitative estimation of this 

 acid fail entirely with the class of salts under consideration. A solution of ter- 

 chloride of gold is reduced only after very long and tedious boiling, and then 

 incompletely. Even after previous reduction of the cobalt to the form of protoxide, 

 the method is found to be very inconvenient and inaccurate. The conversion of 

 the oxalic into carbonic acid by oxidation, and its determination from the weight 

 of this last, gave no better results, inasmuch as the oxidation is effected with 

 difficulty. We have therefore in^all cases had recourse to the ultimate organic 

 analysis, which alone gives reliable results. 



The methods employed in the determination of other substances will be described, 

 when necessary, in treating of particular compounds. 



ROSEOCOBALT. 



The description of the salts of Roseocobalt forms, upon the whole, the most 

 convenient starting point in a statement of the results of our investigation. These 

 salts are in general easily obtained, and the products of their decomposition include 

 several of the other bases, which we shall have occasion to describe. They are 

 almost all well crystallized, and are in gejieral nearly insoluble in cold water, 

 soluble without decomposition in warm water slightly acidulated, but easily 

 decomposed when the neutral solutions are boiled, a hydrated hyper-oxide of cobalt , 

 being thrown down, while free ammonia is given off. The salts of Roseocobalt 

 have a purely saline, not metallic taste ; their color varies, being sometimes dull 

 or brick-red, and sometimes cherry-red. They are usually dichrous, though a few 

 of them do not exhibit this property in a marked degree. Heat decomposes the 

 dry salts readily, the final products of the decomposition being usually ammo- 

 nia, a salt of ammonium and a salt of protoxide of cobalt. Intermediate pro- 

 ducts are, however, sometimes formed, as we shall hereafter see. Thus in many 

 cases the salts of Roseocobalt on boiling yield salts of Luteocobalt, which then, 

 by continued boiling, are completely decomposed. The salts of Roseocobalt may 

 almost always be prepared by the direct oxidation of ammoniacal solutions of salts 

 of protoxide of cobalt, but the particular circumstances, which accompany the 

 formation of each one, will be best considered in treating of the separate com- 

 pounds. Roseocobalt is a triacid base. 



CHLORIDE OP ROSEOCOBALT. 



An ammoniacal solution of chloride of cobalt absorbs oxygen readily from the 

 air, becomes at first brown and then gradually passes through various shades of 

 color to a deep red. The red solution leaves upon a filter a quantity of hydrate of 





