The precipitate
formed is allowed to settle, 50 c.c. of the supernatant solution
is removed with a pipette and transferred to a beaker; 50 c.c. of
decinormal nitric acid and some water is added with sufficient cochineal
tincture. It is then titrated back with decinormal soda; from this is
now readily deducted the amount of carbonic acid, and from that the
MnO_{2}, holding in view that 44 parts of carbonic acid is equivalent to
43.5 of MnO_{2} or 98.87 per cent, and that 1 c.c. of the N/10 baryta
solution is equivalent to 0.0022 grm. of CO_{2}.
If a carbonate, chloride, or nitrate, be present in the native binoxide,
it must be removed with some sulphuric acid. This is afterward
neutralized with a little caustic soda. This method yields the
following results for its value in amount of manganese to 100:
99.91-99.902-99.895, and can be executed in about twenty minutes.
Fifteen determinations can be carried on at once without loss of time,
this, however, depending on the operator's skill. I have made many
assays, and assays by this method with similarly excellent results.
Of the other methods, Bunsen's is acknowledged to be the most accurate,
but is, of course, too troublesome to be used in technical work,
although it is used in scientific analysis.
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