RED COLOUR OF THE PROTOSALTS OF MANGANESE. 309 
examined, from the most different localities, contained more 
or less cobalt, some in such large quantity that it might be 
advantageous to obtain cobalt from them for technical pur- 
poses. I likewise found cobalt constantly present in all the 
red coloured salts of manganese, and the more of it the 
deeper they were coloured. This explains why the so-call- 
ed colourless salt is obtained by heating the protosulphate 
of manganese to redness, since the sulphate of cobalt is rea- 
dily decomposed at a red heat; it further explains why some 
persons have obtained colourless crystals from coloured so- 
lutions by the application of reducing substances, while 
others obtained coloured salts; the latter had probably em- 
ployed material containing cobalt. 
The separation of cobalt from manganese is readily ef- 
fected in the following simple manner: Sulphuret of am- 
monium, diluted with water, is carefully added in drops to 
the somewhat dilute solution of the salt of manganese con- 
taining cobalt, agitating constantly as long as a black pre- 
cipitate is produced. The cobalt is thus completely preci- 
pitated; what first falls contains not a trace of manganese; 
but to be sure of removing the whole of the cobalt, it is ad- 
visable to throw down a little of the manganese with a slight 
excess of sulphuret of ammonium. 
I am not able to confirm the statement met with in some 
works, that colourless salts of manganese are precipitated 
of a white colour by sulphuret of ammonium; at least I al- 
ways obtained the characteristic flesh-coloured precipitate. 
The cause of this statement is undoubtedly to be ascribed to 
the bad nature of the sulphuret of ammonium. Sulphuret 
of ammonium which has been kept fora long time, and con- 
tains, owing to the frequent opening of the bottle, much 
carbonate of ammonia, precipitates protoxide of manganese 
from dilute solutions of a white colour. With ferrocyanide 
of potassium I obtained a white precipitate, which expe- 
rienced no change even after long keeping, while the preci- 
pitate produced by ferrocyanide of potassium in the red 
