Year: 1886

page_text: Date of Application, 18th Sept., 1886.
Complete Left, 20th June, 1887.
Complete Accepted, 16th Sept., 1887.
I FARNHAM MAXWELL-LYTE, of Cotford, Oakhill Road, Putney in the County of
Surrey, Analytical Chemist do hereby declare the nature of this Invention to be as
follows:-
My Invention relates to the manufacture of basic lead salts for use as pigments and
it consists mainly in an improvement in the process for which I made application for
Letters Patent No. 10298 of 1886. I have found that pigments produced in the
manner set forth in the provisional Specification of my said application are materially
improved by pressure, or friction, or the two combined, which may be applied in any
suitable manner, so long as increased density is thus produced; i.e. the pressure and
friction may be obtained by grinding under edge runners.
The best results are obtained by treating the materials in a dry state, but I may
also treat them in a moist state. Pigments treated as thus described, appear to have
an increased density and covering power and at the same time require less oil or other
vehicle.
I would have it understood that although I have referred above to the treatment of
basic lead salts produced according to my previous application; this precess of densifying
is also applicable to pigments produced according to the modification which I will now
describe.
I find that insoluble or sparingly soluble basic salts of lead may be converted into
other basic or sparingly soluble salts of lead by treatment with a solution of a soluble
salt, the acid of which, corresponds to the acid of the basic salt of lead it is desired to
produce.
When working according to this and my previous application, with say, a basic
acetate of lead which I use in preference (though I do not limit myself thereto) to the
other soluble basic salts of lead, I find the most practical method is to precipitate with
the requisite acid or acids, until such time as all the extra base is thrown down or
until the solution is just acid to litmus-e.g. if I have precipitated the extra base, out
of say, one gallon, I add one more gallon wherewith to render basic the precipitate by
digestion, or I add whatever further quantity I find by experience requisite to bring
the salt to the required state of basicity when digested for a given time, and with a
1

page_text: liquor of a proper degree of concentration. I may also always employ solutions of a given
strength of basicity; then provided the solution added for the purposes of digestion is
of similar chemical composition to that from which the salt was precipitated I can
always depend on obtaining with certainty similar results at each successive operation.
This similarity of composition is easily effected by preparing a vat of basic acetate
containing (say) 100 gallons, and withdrawing (say) 40 gallons for precipitation, and
then (say) 40 more for digestion, or that quantity which I have found by experience
to answer best.
When the precipitate from this is sufficiently digested, the effluent therefrom may
be returned to (say) the same vat, and by judicious additions of acetic acid and water
be brought in the form of a normal salt to that degree of specific gravity which has
been found to answer best for the formation of a basic salt most favourable for digesting
the precipitate; or if only a trifling loss of acetate has taken place the same may with
water be brought up in bulk to 100 gallons-should the washings of the precipitates
not compensate for the loss by evaporation, and then be converted by the usual
method with granulated lead into a mixture of diplumbic and triplumbic acetate.
These methods of working may of course be varied in detail but I find
uniform results are in this way obtained when working on a practical scale. In
the production and treatment of precipitates and materials as herein-described, I find
as recited in my previous application for provisional protection, the employment of heat
to be advantageous.
D117
.ni 1
1000
F. MAXWELL LYTE.
By A. M. & Wm. Clark,
53, Chancery Lane, London,
Patent Agents.

page_text: I, FARNHAM MAXWELL LYTE of Cotford, Oakhill Road Putney in the County of
Surrey Analytical 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 :-
My Invention relates to the manufacture of basic lead salts for use as pigments;
and it consists in an improvement in the method of working the process for which 1
made application for Letters Patent on August 11th 1886 No. 10298.
The object of the present invention is to enable the operator to readily ascertain the
quantity of base contained in the soluble basic lead salt employed necessary to impart
the required degree of basicity to the precipitated lead salts, so that the operation may
be carried out with such accuracy as to always ensure a practical and commercially
valuable result.
The following is an example of a method of carrying out my process:-I take, say,
about 100 gallons of basic lead acetate (made for instance by repeatedly pouring a
neutral lead acetate of, say, specific gravity 1.15 at 60° Fahr. over finely divided lead)
of specific gravity about 1.315 at 60° Fahr., and I precipitate the said 100 gallons
with, say,
sulphuric acid until the liquid becomes so barely acid that it will turn litmus
paper plum color. I then heat this acidulated liquor (say to boiling point in a steam
jacketted pan) and after allowing about an hour for the precipitate to settle, I decant
the acidulated effluent. This effluent may again be rendered basic by pouring it over
finely divided lead, as above described; a further quantity of acetic acid being added,
if necessary. To the lead sulphate precipitate left in the pan, I then add a further
quantity (say 50 gallons more or less, according to the basicity it is required to impart
to the precipitate) of the same basic acetate, that is to say, having in the first instance
precipitated all the extra base out of 100 gallons of a given basicity I then add to the
precipitate another measure of liquor containing a given proportion of base. I then
proceed to heat this liquor (containing the precipitated sulphate) preferably to
212° Fahr. and continue boiling and stirring for about a quarter of an hour. By this
time, it will be found that the sulphate has attained its right degree of basicity, the
liquor on the other hand, having lost most of its extra base.

page_text: Having now particularly described and ascertained the nature of the said invention
and in what manner the same is to be performed, I declare that what I claim is ;-
The herein described volumetric method of carrying out the herein described
process of treating lead salts, whereby the required degree of basicity may be imparted
to a given quantity of precipitated lead salt.
F. MAXWELL LYTE.
By. A. M. & Wm. Clark,
53, Chancery Lane, London,
Patent Agents.