ne is deposited from a solution of lead containing small
quantities only of free nitric acid.

The lead peroxide deposited is at first light brown or dark red, and
becomes constantly darker and finally taking a velvet-black. As its
stratification upon the platinum is unequal, it forms beautifully
colored rings.

Experiments show that the quantity of peroxide deposited depends on
the nature of the solution and the strength of the current. In case of
very feeble currents and slight acidity, its quantity is so small that
it does not need to be taken into consideration. If the lead solution
is very dilute scarcely any current is observed, lead solutions _per
se_ being very bad conductors of electricity.

Faintly acid concentrated lead solutions give loose peroxide along
with much spongy metallic lead. Free alkali decreases the separation
of peroxide; feebly alkaline solutions, concentrated and dilute, yield
relatively much peroxide along with metallic lead, while strongly
alkaline solutions deposit no peroxide.

Dried lead peroxide is so sparingly hygroscopic that it may be weighed
as such; its weight remains constant upon the balance for a long time.
In order to apply the peroxide for quantitative determinations, a
large surface must be exposed to action. As positive electrode a
platinum capsule is convenient, and a platinum disk as negative pole.
The capsule shape is necessary because the peroxide when deposited in
large quantities adheres only partially, and falls in part in thin
loose scales. It is necessary to siphon off the nitric solution,
since, like all peroxides, that of lead is not absolutely insoluble in
nitric acid. The methods of Riche and May give results which are
always too high, since portions of saline solution are retained by the
spongy deposit and can be but very imperfectly removed by washing.
This is especially the case in presence of free alkali.

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