separation of iron from other metals . 299 
in the air, and proved to be mere oxide of manganese, un- 
contaminated by iron, and amounting to half a grain. 
Manganese has been suspected in various species of cast 
iron ; and though Mr. Mushet's experiments go to prove 
that it does not usually enter in abundance, they can hardly 
be regarded as establishing the fact of its absence. It might 
not be uninteresting to resume the investigation with the 
aid of a mode of analysis so well adapted to experiments 
on a large scale, as I have no doubt that, with proper care, 
one part in a thousand, or even less, of manganese might be 
insulated from iron. 
The separation of iron from uranium cannot be accom- 
plished by the process above described, that metal possessing 
a property analogous to that which forms the subject of this 
paper. By inverting the process, however, we shall succeed 
even here. A mixed solution of iron and uranium being 
de-oxidized by a current of sulphuretted hydrogen, and then 
treated with an earthy carbonate, the iron passes in solution 
while the uranium separates. This difference in the habitudes 
of the two oxides of iron presents us in fact with a kind of 
chemical dilemma, of one or the other of whose horns we 
may avail ourselves in any proposed case. In studying the 
habitudes of uranium, however, I have met with some anoma- 
lies which require farther investigation. Zirconia too might 
probably be freed from iron with equal facility by a similar 
inversion of the process ; but this I have not yet had an op- 
portunity of trying satisfactorily. 
J. F. W. HERSCHEL. 
London, 
April 4, 1821. 
MDCCCXXI. 
Qq 
