The manganese sulphide is then ignited in
a current of hydrogen, and weighed as such.
SEPARATION OF IRON AND ALUMINUM.
The quantitative separation of iron from aluminum, which presented many
difficulties according to the older methods, may be easily performed
by electrolysis. If a solution of iron ammonium oxalate and aluminum
oxalate, to which an excess of ammonium oxalate has been added, be
submitted to the action of the electric current, the iron will be
deposited as a firmly adhering coat on the negative electrode, while
the aluminum oxide remains in solution, just so long as the quantity
of ammonium oxalate is in excess of the quantity of ammonium carbonate
produced. When, finally, a precipitation of aluminum oxide takes place
the liquid is almost free from iron. From time to time, the solution, in
which the aluminum oxide is suspended, is tested for iron by ammonium
sulphide, and the current is interrupted when no further reaction is
observed. The best method of procedure is to add ammonium oxalate in
excess to a neutral, a slightly acid solution, or to one which has been
neutralized by the addition of ammonium hydrate (a hydrochloric acid
solution is not well adapted for this purpose); then as much more solid
ammonium oxalate is added until for every 0.
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