c. measuring
flask.
3. A dilute, carefully standardized solution of permanganate of
potassium.
The method of using these solutions is as follows: 100 c.c. of No. 1
and No. 2 are measured off (each solution in its own measuring flask),
brought together in a covered beaker glass, and acidified with dilute
sulphuric acid. The excess of oxalic acid is then determined by means
of solution No. 3.
When it is desired to make a determination of nitric acid, 100 c.c. of
solution No. 1 are measured off, and as much of it as may be
convenient is poured into the tubes, E, E, together with about a
gramme of zinc sulphate for each tube, which substance appears to
considerably facilitate the absorption of the nitric oxide by the
permanganate. When the operation is over, the contents of E, E are
poured into a beaker glass. 100 c.c. of solution No. 2 are then
measured off, and a portion, together with a little sulphuric acid,
poured into E, E, to dissolve the oxide of manganese which has
separated during the absorption of the nitric oxide. The oxide having
been dissolved, the liquid in E, E, and the rinsings of the tubes,
also the residues of permanganate and oxalic acid left in the
measuring flasks, and the rinsings from these, are all brought
together in the same beaker glass. Finally, the amount of solution
No.
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