METHOD OF SEPARATING COBALT AND NICKEL.
The following method of separating and estimating cobalt and nickel has
been described by Mr. James Hope,[125] with whom it has been in daily
use for several years with completely satisfactory results.
The quantity of ore taken should contain about .5 gram of the mixed
metals. It is dissolved in hydrochloric acid or aqua regia, and the
solution evaporated to dryness. The residue is taken up with dilute
hydrochloric acid and hot water. The solution is filtered off from the
silica, freed from second group metals by treatment with sulphuretted
hydrogen and filtered, and after oxidation with nitric acid is separated
from iron and alumina by the basic acetate method (page 233). The
precipitate is redissolved in a little hydrochloric acid, and again
precipitated by sodium acetate. The two filtrates are mixed and treated
with a little acetic acid, and the cobalt and nickel are then
precipitated as sulphides by a current of sulphuretted hydrogen. The
precipitate is filtered off, washed, dried, and calcined, and the
resulting oxides are weighed to get an idea as to the quantity of the
two metals present.
The calcined precipitate is dissolved in a small covered beaker in aqua
regia with the help of a few drops of bromine to remove any separated
sulphur, and the solution evaporated to dryness with a few drops of
sulphuric acid.
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