[Illustration: LEAD BEING TAKEN OUT OF THE STACKS.
The next step is to take an earthenware vessel, which resembles an
ordinary stone crock, and first pour into it a small quantity of acetic
acid, which is about the same as table vinegar. Then the crock or pot
is filled up with the lead buckles.
Where this white lead is made in a large way many thousands of these
pots are placed in a building, the sides of which are walled up tight,
the spaces between the crocks being filled in with tan bark. After
the floor has been covered with a layer of these crocks, the layer is
covered with boards, in order to provide a foundation for setting in
the next layer of crocks and tan bark. The layer of boards also serves
as a floor to keep the tan bark from falling into the open crocks on
the tier below. This procedure is followed with tier after tier until
the building is completely filled.
Corrosion of the metallic lead in the pots now begins, because the tan
bark generates some heat, becoming finally quite warm. This heat causes
the acetic acid or vinegar to throw off vapor or steam, which attacks
the metallic lead, causing it to decompose or corrode. This process
goes on for many weeks (sometimes as much as fifteen or sixteen weeks),
until those buckles of metallic lead have become a mass of white powder
and nearly all trace of the original metallic lead has disappeared.]
[Illustration: A LEAD BUCKLE AFTER CORROSION.]
[Illustration: A LEAD BUCKLE BEFORE CORROSION.]
[Illustration: HOW OXIDE OF ZINC IS OBTAINED