on the Ammonia-cobalt Bases. 249 
. 
ond part of our memoir. 
_ Strong sulphuric acid digested with sulphate of Roseocobalt 
yields, under some circumstances, sulphate of ammonia and sul- 
phate of Luteocobalt. In other cases it yields the acid sulphate 
of Purpureocobalt. By double decomposition with salts of ba- 
sq the sulphate of Roseocobalt yields the other salts of this 
ase. 
The reactions of the sulphate are somewhat different from 
those of the chlorid, as will be seen from the following statement, 
Ferrideyanid of potassium gives no precipitate at first, but 
after two’ hours very distinct and well defined small augitic 
crystals, 
Cobaltideyanid of potassium behaves in a precisely similar 
Manner, giving red crystals. 
; Neutral chromate of potash gives no precipitate. The bichro- 
mate gives none at first, but after two or three hours, groups of 
reddish brown needles. 
We shall hereafter state our reasons for believing that in cer- 
fain cases there is a conversion of the triacid Roseocobalt in the 
Sulphate of this base, into the biacid Purpureocobalt. 
ANHYDROUS NITRATE OF ROSEOCOBALT. } 
The ammoniacal solution of nitrate of cobalt absorbs oxygen 
very readily from the air, and the oxydation is lete 
nitrate of Luteocobalt is formed under these circumstances, and 
being insoluble in the ammoniacal liquid, forms a bright yellow 
talline precipitate upon the bottom and sides of the vessel. 
During the process of the oxydation, crystals of the compound de- 
puibed by Frémy as the nitrate of Oxycobaltiaque are quai 
Tmed in some quantity, but these disappear at a later stage of 
the oxydation, when the liquid takes a deep wine-red color. 
© crystals of nitrate of Oxycobaltiaque were first observed by 
Leopold Gmelin, a 
fumed them, though Frémy’s analyses do not appear to us satis- 
ry, 
fac 
