1. A solution of permanganate such that one c.c. is equivalent to
about fifteen milligrammes of nitrate of potassium, according to the
reaction:
KMnO_{4} + NO = KNO_{3} + MnO_{2}.
This solution is employed for the absorption of the nitric oxide. Its
strength need not be exactly known. There is no objection to a more
concentrated solution, except that which pertains to all strong
standard solutions, namely, that a small error in measurement would
then give a larger error in the results. 100 c.c. of this solution are
required for each determination, and the measurement is always made in
one and the same 100 c.c. measuring flask, which, if necessary, should
be labeled to distinguish it from that used for solution No. 2.
2. A solution of oxalic acid which is very slightly stronger than that
of the permanganate just described--that is, a solution such that one
c.c. of it will somewhat more than decompose one c.c. of the
permanganate, according to the reaction:
2KMnO_{4} + 3H_{2}SO_{4} + 5C_{2}H_{2}O_{4}.2H_{2}O =
K_{2}SO_{4} + 2MnSO_{4} + 18H_{2}O + 10CO_{2}.
The exact strength of this solution need not be known, since we only
require the difference in value between it and solution No. 1, which
is determined by means of solution No. 3. 100 c.c. of this solution
are also required for each determination, and the measurement, as in
the preceding case, is always made in the same 100 c.
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