Mr. J. F. W. Herschel on the 
294 
whole of the iron to the last atom, is precipitated, and the 
whole of the other metals present (which I suppose to be 
manganese, cerium, nickel, and cobalt), remains in solution. 
The precautions necessary to ensure success in this process 
are few and simple. In the first place, the solution must 
contain no oxide of manganese or cerium above the first de- 
gree of oxidation, otherwise it will be separated with the 
iron. It is scarcely probable in ordinary cases that any such 
should be present, the protoxides only of these metals form- 
ing salts of any stability ; but should they be suspected, a 
short ebullition with a little sugar will reduce them to the 
minimum. If nitric acid be now added, the iron alone is per- 
oxidized, the other oxides remaining at the minimum.* More- 
over, in performing the precipitation the metallic solution 
should not be too concentrated, and must be agitated the 
whole time, especially towards the end of the process ; and 
when the acid reaction is so far diminished that log-wood 
paper is but feebly affected by it, the alkaline solution must 
be added cautiously, in small quantities at a time, and in a 
diluted state. If too much alkali be added, a drop or two 
of any acid will set all right again ; but it should be well ob- 
served, as upon this the whole rigour of the process depends, 
that no inconvenience can arise from slightly surpassing the 
point of precise neutralization, as the newly precipitated car- 
* Dr. Forsch ammer, in a paper recently published in Thomson’s Annals of 
Philosophy, contends that the proto-salts of manganese are absolutely void of co- 
lour. To this I can only say, that 1 have not succeeded in depriving the muriate 
of its pale rose colour by any length of ebullition with sugar or alcohol, after which, 
however, not a trace of deutoxide could be detected in it. I cannot help regarding 
the process here proposed for freeing manganese from iron as preferable to that of 
Dr. F. 
