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.
_Thallium_ behaves similarly to lead. From a nitric acid solution it
is thrown down, according to the proportion of free acid, either as
sesquioxide only or in small quantities as silvery, metallic leaflets;
from alkaline solutions it is deposited as sesquioxide and metal, the
latter of a lead-gray color. Thallium solutions conduct the electric
current badly.
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