Improvements in the Manufacture of Lead Pigments.
Year: 1893

page_text: Date of Application, 12th July, 1893
Complete Specification Left, 11th Apr., 1894-Accepted, 28th Apr., 1894
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Lead Pigments.
I HENRY RICHARD GREGORY, of 5 Amerland Road, Wandsworth, in the
County of Surrey, Chemist, do hereby declare the nature of this invention to be as
follows:-
I take sulphate of lead preferably that made by volatilization, and add to it, in a
vessel capable of being heated by steam or any suitable method water and caustic
soda or potash or ammonia in any suitable proportion, the quantity depending upon
the amount of conversion required, varying from about 10% of the sulphate of lead.
If
The mixture is then boiled until it gives no alkaline reaction to test paper.
ammonia is used it will be necessary to carry out the boilings in a close vessel to
prevent loss of ammonia which can be afterwards recovered from the solution by
any suitable method. By this method a proportion of the sulphate of lead is
converted into hydrated oxide of lead and is in intimate combination with the
unconverted sulphate. The mixture is well washed with water and dried at a
moderate heat and is then suitable for use as a pigment being ground with oil in
the usual manner.
The hydrated oxide of lead produced by this method enables the mixture to
possess the requisite body and opacity peculiar to white lead made by the Dutch
process.
Dated this 12th day of July 1893
HENRY RICHARD GREGORY.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Lead Pigments.
I, HENRY RICHARD GREGORY, of 5 Amerland Road, Wandsworth in the
County of Surrey, Chemist, 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:-
I take sulphate of lead preferably that made by volatilization, and add to it, in a
vessel capable of being heated by steam or any suitable method say five times its
weight of water the mixture is raised to a boiling temperature and a solution of
caustic soda in say five times its weight of water is added the quantity of the soda
depending upon the amount of conversion required. I find about 10 parts by
weight of soda to 100 parts of sulphate of lead to be suitable for most purposes
more may however be used but this adds to the cost and is usually unnecessary,
less than eight per cent. should never be used. Equivalent quantities of caustic
potash or ammonia may be substituted for the soda. The mixture is then boiled
for about 15 minutes or until it gives no alkaline reaction to test paper.
reaction between the sulphate of lead and alkali may be carried out in the cold
but it takes several hours and the product is not so perfect for use as a pigment.
If ammonia is used it will be necessary to carry out the boilings in a close vessel
to prevent loss of ammonia which can be afterwards recovered from the solution
by any suitable method. By this method a proportion of the sulphate of lead is
converted into hydrated oxide of lead and is in intimate combination with the
unconverted sulphate. The mixture is well washed with water pressed and dried
Price 8d 1
The

page_text: at a moderate heat and is then suitable for use as a pigment being ground with oil
in the usual manner.
The hydrated oxide of lead produced by this method enables the mixture to
possess the requisite body and opacity peculiar to white lead made by the Dutch
process.
If the sublimed sulphate of lead is of a bad colour as is sometimes the case I
boil it before conversion in about five times its weight of water containing
one per cent. of sulphuric acid and one per cent. of hydrochloric acid for about an
hour and wash it to remove the acid.
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
1. The process of manufacturing white lead consisting in treating sulphate of
lead with not less than eight per cent. of its weight of caustic soda or an equivalent
quantity of caustic potash or ammonia substantially as described.
2. The process of manufacturing white lead consisting in treating sulphate of
lead made by volatilization with not less than eight per cent. of its weight of
caustic soda or an equivalent quantity of caustic potash or ammonia substantially
as described.
3. The manufacture of lead pigments substantially as described.
D
14
of March 1901
HENRY RICHARD GREGORY.