Process for the Manufacture of Oxide of Lead and of White Lead from Crude Sulphate of Lead.
Year: 1892

page_text: Date of Application, 9th Sept., 1892
Complete Specification Left, 3rd May, 1893-Accepted, 12th Aug., 1893-
PROVISIONAL SPECIFICATION.
Process for the Manufacture of Oxide of Lead and of White Lead
from Crude Sulphate of Lead.
I, PAUL BRONNER, Philosophiae Doctor, Stuttgart, in the Empire of Germany,
Gentleman, do hereby declare the nature of this invention to be as follows:-..
Crude sulphate of lead occurring in cotton printing works, and mostly of a
yellowish or brownish colour, always contains, besides the solution of acetate of
aluminium adhering to it, a small quantity of basic aluminium salts, which owing to
their dissolving with great difficulty in water, cannot be eliminated completely
by mere washing and also certain indissoluble organic colouring matter originating
from the tar contained in wood vinegar.
I now mix the sulphate of lead with a little sulphuric acid adding sufficient water
so as to form a thin sort of cream, heat the mixture to boiling point by introducing
steam, wash the whole and sift. The sulphate of lead now contains no other
impurities but the above mentioned organic bodies.
The sulphate of lead is then digested with a solution of carbonate of soda (or
with carbonate of soda and caustic soda) by which process a carbonate of lead is
obtained. I wash the latter, dry it and then anneal it: the carbonate of lead is now
changed into oxide of lead, free from iron and copper. This oxide of lead is very
suitable for all purposes especially for cristal glass, for glazing in faience works, for
minium etc.
In order now to produce white lead, I follow Thénard's method, i.e. digest the
oxide of lead with a solution of sugar of lead, which dissolves the former very
readily, and decompose the solution of basic acetate of lead by a jet of carbonic
acid. The solution of sugar of lead lying on the top of the precipitated white
lead is then again digested with the same quantity of oxide of lead as before
and so on.
By this simple and cheap method, crude sulphate of lead which hitherto, owing
to its yellowish or brownish tint, was unsuitable for colours and could only be used
by reducing it to metallic lead in the furnace, may be converted into pure oxide of
lead or in white lead of the best quality.
The mud of the lead chambers in sulphuric acid manufactories, as it does not
require being previously treated with sulphuric acid, must be washed well in water
and digested after with carbonate of soda (or with carbonate of soda and caustic
soda) and then be treated as described here before.
Dated this 6th day of September 1892.
COMPLETE SPECIFICATION.
Process for the Manufacture of Oxide of Lead and of White Lead
from Crude Sulphate of Lead.
I, PAUL BRONNER 3 Kerner Strasse Stuttgart Germany Philosophia Doctor
do hereby declare the nature of this invention and in what manner the same is to
be performed, to be particularly described and ascertained in and by the following
statement:-
Crude sulphate of lead occurring in cotton printing works and mostly of a
yellowish, brownish or greenish colour, always contains, besides the solution of
acctate of aluminium (or acetate of chromium respectively) adhering to it, a small
quantity of basic aluminium salts (or basic chromium salts), basic sulphate and
basic acetate of aluminium (or of chromium respectively) and generally also the
ID 11

page_text: respective iron salts, originating from the. iron which the alum (or the sulphate of
aluminium) contains, used for the red mordant. ("mordant rouge"); and also,
which is the worst, certain colouring, indissoluble, organic bodies, originating from
the tar of the wood vinegar that has been used for the making of the sugar
(acetate) of lead. The above mentioned basic salts being dissolving in water with
the greatest difficulty, cannot be removed by washing; they must, therefore, be
changed into neutral easily dissolving salts.
I now mix the crude sulphate of lead with a little sulphuric acid, adding
sufficient water so as to form a thin sort of cream. I heat the mixture to boiling
point by introducing steam wash the whole and sift. Now the aluminium salts
(or chromium salts respectively) and iron salts are completely removed, but there
are still partially the substances of tar; but the latter can only be entirely removed
by higher temperature with oxide of lead.
The sulphate of lead is then digested with a solution of carbonate of soda, by
which process a solution of sulphate of soda (Glauber's salt) and a precipitate of a
carbonate of lead is obtained. I wash the latter, dry it and anneal it lightly, eg,
in a mule. By this calcination, the carbonate of lead is decomposed, the mentioned
organic matter destroyed and a small quantity of metallic lead originates. If the
air is admitted, the minutely distributed lead readily oxidizes again in the high
temperature absorbing the oxygen of the air. I have now pure oxide of lead, free
from iron, copper and antimony, very appropriate for all purposes, especially for
making crystal glass, for glazing in faïence works, for minium and white lead.
in the calcination of the carbonate of lead the air is not admitted, this oxide of
lead will contain a small quantity of metallic lead, which however does not
damage its use.
If
In order to produce white lead several methods can be followed, but the method
of Thénard furnishes the best quality. Thus digest the oxide of lead with a
solution of sugar of lead, which dissolves the former very readily and decompose
the solution of basic acetate of lead by a jet of carbonic acid. The solution of
sugar of lead, lying on the top of the precipitated white lead, is then again digested
with the same quantity of oxide of lead as before and so on.
There is indeed another method. You may make a thin cream of the oxide of
lend by a solution of lead sugar and decompose the cream-not the solution-by
introducing carbonic acid. But the quality of the white lead produced in this way
is very inferior to the product of the former method.
By this simple and cheap method crude, sulphate of lead, which hitherto owing
to its yellowish, brownish or greenish tint, was unsuitable for colours and could
only be used by reducing it to metallic lead in the furnace, may be converted into
pure oxide of lead or into white lead of the best quality.
The mud of the lead chambers in sulphuric acid manufactories, as it does not
require to be previously treated with sulphuric acid, must be washed well in water
and digested after with carbonate of soda and then be treated as described
hereinbefore.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
The process of manufacturing pure oxide of lead and white lead from crude
sulphate of lead, which consists in boiling it, if necessary, with diluted sulphuric
acid, then washing it and treating it with a solution of carbonate of soda, annealing
of the carbonate of lead, then digesting the produced pure oxide of lead with a
solution of sugar of lead, and ultimately precipitating the basic acetate of lead with
carbonic acid, all substantially as described.
Dated this 21st day of April 1893.
PAUL BRONNER,
Philosophie Doctor."