Improvements in and connected with the Treatment of Lead Sulphate for Use as a Pigment.
Year: 1893

page_text: Date of Application, 12th May, 1893
Complete Specification Left, 12th Mar., 1894-Accepted, 12th May, 1894
PROVISIONAL SPECIFICATION.
Improvements in and connected with the Treatment of Lead
Sulphate for Use as a Pigment.
WILLIAM VIRGO WILSON, Consulting Chemist May Bank Margery Park
Road Forest Gate London E. and JOHN JAMES LUNDY 56 Leadenhall Street
London Manufacturing Chemist do hereby declare the nature of this invention
to be as follows:-
The improvement of sulphate of lead, prepared by any of the well known
processes by associating the same with hydrated lead oxide.
Although it is well known that hydrate of lead oxide may be made by
precipitating a soluble salt of lead with caustic potash, soda or ammonia, we
prefer to prepare this body, either by continuously heating lead carbonate in contact
with water or steam by which a large proportion of the lead carbonate is converted
into lead bydrated oxide or we form this material by acting upon finely divided
anhydrous lead oxide with glycerine, glucose or sugar or with a mixture of one
with the other or all of them, in the cold or with the application of heat, until the
lead oxide is converted into its hydrate.
The hydrated lead oxide, when mixed with lead sulphate, gives to this body an
improved covering power.
These reactions may be conducted in the presence of the lead sulphate instead of
making the hydrated lead oxide separately and subsequently mixing them.
Dated this 12th day of May 1893.
W. V. WILSON.
JOHN J. LUNDY.
COMPLETE SPECIFICATION.
Improvements in and connected with the Treatment of Lead
Sulphate for Use as a Pigment.
We, WILLIAM VIRGO WILSON of May Bank, Margery Park Road, Forest
Gate London, Consulting Chemist and JOHN JAMES LUNDY of 56 Leadenhall
Street London E.C. Colour Manufacturer 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 :-
The object of this invention is the improvement of sulphate of lead to be used
as a pigment by associating the same with hydrated lead oxide.
The hydrated lead oxide may be made in any convenient or suitable way for
example by treating a salt of lead with caustic potash, soda or ammonia but we
prefer to prepare this body either by continuously heating lead carbonate in contact
with water or steam by which a large proportion of the lead carbonate is converted
into hydrated lead oxide.
The hydrated lead oxide when mixed with lead sulphate gives to this body
an improved covering power.
The formation of the hydrated lead oxide may be conducted in the presence
of the lead sulphate instead of making the hydrated lead oxide separately and
subsequently mixing them.
For example the hydrated lead oxide may be made from a portion of the lead
sulphate itself.

page_text: The following are examples of the ways in which the pigment may be formed
according to this invention but we do not limit ourselves to the precise details of
these examples.
EXAMPLE 1.
In forming the pigment by the direct admixture of sulphate of lead with
hydrated lead oxide it is preferred that they be used in the proportions of two
equivalents of sulphate of lead to one equivalent of hydrated lead oxide and so
that the pigment shall consist of 304 parts by weight of sulphate of lead to
120-5 parts by weight of hydrated lead oxide. We do not confine ourselves to
these proportions but if they be greatly departed from either by lessening or
increasing the quantity of hydrated lead oxide the body or covering power of the
pigment is not improved.
The sulphate of lead and hydrated lead oxide should be thoroughly incorporated
or intimately mixed with each other. This may be done for example by grinding
them together.
EXAMPLE 2.
The process of forming the pigment by conducting the reactions in which the
hydrated lead oxide is formed in the presence of the sulphate of lead may be carried
out for example by converting a portion of the sulphate of lead into lead carbonate
by treating it with an alkaline carbonate in solution in such quantity, as to
convert only a portion of the sulphate of lead into lead carbonate and after
washing away the alkaline sulphate formed in the reaction the lead carbonate may
be heated in the presence of water or steam so as to convert it into hydrated. lead
oxide. This operation of applying heat may be performed in an open vessel or for
higher temperatures in a closed vessel under pressure the conversion being
accelerated by the latter process. Or a portion of the sulphate of lead may be
converted into hydrated lead oxide by treating the sulphate of lead for example
with caustic soda or potash in solution and after washing away the sodic or other
sulphate formed in the reaction the hydrated lead oxide will be left in association
with the lead sulphate.
The substances employed should be well agitated and the pigment when formed
should be thoroughly dried.
It is preferred that the materials employed in the reactions should be used in
such quantities as will bring the hydrated lead oxide in association with the sulphate
of lead in the proportions mentioned in Example 1.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed I declare that what we
claim is :-
The preparation or treatment of sulphate of lead as a pigment by associating
the same with hydrated lead oxide whether the hydrated lead oxide be formed
separately from the sulphate of lead or in the presence of, or from part of, the
sulphate of lead as hereinbefore explained.
Dated this 12th day of March 1894.
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