The author has proceeded as follows: The lead peroxide is dried in the
capsule, and there is passed over it pure dry gaseous sulphurous acid
in a strong current from a rather narrow delivery tube. Lead sulphate
is formed with evolution of heat; it is let cool under the exsiccator,
and weighed as such. Or he ignites the peroxide along with finely
pulverized ammonium sulphite; the mass must have a pure white color.
After the conclusion of the reaction it is ignited for about 20
minutes. The results are too high. The proportion of actual lead
peroxide in the deposit ranges from 94 to 94.76 per cent. The peroxide
precipitated from a nitric solution may, under certain circumstances,
be anhydrous. This result is due to the secondary influences at the
positive pole, where the free acid gradually withdraws water from the
peroxide.

The peroxide thrown down from alkaline solutions retains alkali so
obstinately that it cannot be removed by washing; the peroxide plays
here the part of an acid. The lead nitrate mechanically inclosed in
the peroxide is resolved by ignition into oxide, hyponitric acid, and
oxygen; this small proportion of lead oxide does not exert an
important influence on the final result. The quantity of matter
mechanically inclosed is relatively high, as in the precipitation of
much lead peroxide there is relatively more saline matter occluded
than when a few centigrammes are deposited. The peroxide incloses also
more foreign matter if it is thrown down upon a small surface than if
it is deposited in a thin layer over a broad surface. From numerous
analyses the author concludes that in presence of much free nitric
acid the proportion of water is increased; with free alkali the
reverse holds good.