--Group III. and sesqui. iron are
separated by agitation with baryta carbonate, some chloride of ammonia
being added to prevent nickel and cobalt precipitation traces, and
filtering. If cobalt is present we treat this filtrate with nitrite
of potassa, etc., to separate it (that is, if it and nickel are to
be separated and estimated in the same sample; but if they are to be
estimated as one, or not separated, the treatment with nitrite, etc.,
is not used). The filtrate from this last is directly treated with
chlorine. If nickel and cobalt are not to be estimated in this sample,
the solution, as chlorides, is mixed with some chloride of ammonium
and ammonia, then with a fair excess of phosphoric acid, a sufficient
quantity more of ammonia to render the mixture alkaline. The precipitate
formed is transferred to the filter and well washed with water
containing NH_{3}Cl and NH_{4}O, then dissolved in hydrochloric acid
and reprecipitated with ammonia, filtering and washing as before. It is
again dissolved in HCl and titrated with uranium solution, or decomposed
by tin, as noted below, and the manganese precipitated as binoxide with
chlorine, and determined.
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