Improvements in Making White Lead.
Year: 1894

page_text: Date of Application, 17th May, 1894
Complete Specification Left, 13th Mar., 1895-Accepted, 13th Apr., 1895
Improvements in Making White Lead.
I, JOHN STEWART MACARTHUR, of 589, Shields Road, in the County of the
City of Glasgow, North Britain, Technical Chemist, do hereby declare the nature
of this invention to be as follows, that is to say :—
My said invention has for its object the making of white lead in an improved and.
economical manner.
In carrying out my invention I form a solution of Rochelle salt or other alkali
tartrate and heat it to a temperature at or near its, boiling point. To the hot
solution I add litharge or other oxide of lead, and agitate the mixture to prevent
settling of the oxide of lead and to facilitate the intended reaction. After
undissolved residues have been separated by filtration or otherwise, carbonic acid is
passed through the solution which is maintained at the temperature hereinbefore
indicated. The carbonic acid may be derived from any convenient source, such as
fire gases. The lead in solution is gradually precipitated as carbonate which may
be used as ordinary white lead, after separation from the liquid, and purification
and drying by known means. The solution and washings from which the lead
carbonate has been separated may be used again indefinitely, after concentration by
evaporation, if necessary.
Instead of tartrates other salts having somewhat similar properties may be used,
such as citrates and oxalates, but I believe the tartrates to be preferable.
Dated this Sixteenth day of May 1894.
EDMUND HUNT,
Applicant's Agent.
Improvements in Making White Lead.
I, JOHN STEWART MACARTHUR, of 589, Shields Road, in the County of the
City of Glasgow, North Britain, Technical 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, that
is to say:
The object of my invention is the making of white lead in an improved and very
economical manner; and in carrying out my invention I first prepare a solution of
a tartrate of soda or of potash or of a mixture of these alkalies or of the double
tartrate known as Rochelle salt. The solution which should be neutral or slightly
alkaline (such alkalinity being by preference produced by the addition of caustic
soda or caustic potash) may contain from 10 to 20 parts of tartrate to every
1,000 parts of water, 14 parts of tartrate yielding very good results. To the
solution heated to about its boiling point I add an oxide of lead by preference
massicot or litharge. The other oxides of lead as ordinarily met with in commerce
are to a certain extent soluble in the solutions specified; and to the extent to which
they are soluble can be used for the purposes specified but the most advantageous
Price 8d1

page_text: forms and compositions of oxide to use and those which I prefer to use are massicot
or litharge, I agitate the mixture to prevent settling of the oxide, and to facilitate
the intended reaction. Or I cause the solution to percolate through a layer of the
lead oxide of moderate depth, say a depth of about two inches. When the oxide
of lead or most of it has become dissolved, undissolved residues are separated by
filtration or otherwise; and carbonic acid is passed through the solution, which is
maintained at the temperature hereinbefore indicated. The carbonic acid may be
derived from any convenient source such as fire gases, but should be free from dust
or other solid impurities and from other gas which is not inert. The water
employed is preferably as free from color as is conveniently possible.
The lead in solution is gradually precipitated as carbonate or white lead, which
may be used as ordinary white lead, after separation of the liquid, and purification
and drying by known means. The solution and washings separated from the white
lead, may be used again indefinitely, after concentration by evaporation if
necessary.
Instead of passing carbonic acid through the solution it will be sufficient when
speed is not an object for it to be present in the atmosphere in contact with the
surface of the solution, and as the lead oxide becomes gradually converted into
white lead more lead oxide may be added from time to time.
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 for making white lead in which lead oxide is dissolved in a solution
of a tartrate of soda or of potash or of a mixture of these alkalies, or of the double
tartrate known as Rochelle salt at or about a boiling temperature, and is
subsequently treated with carbonic acid during which treatment the liquid is
maintained at about a boiling temperature substantially as hereinbefore described.
Dated this Twelfth day of March 1895.
EDMUND HUNT,
Applicant's Agent.