Improvements relating to the Manufacture of White-lead and to Apparatus for use therein.
Year: 1891

page_text: Date of Application, 5th June, 1391
Complete Specification Left, 5th Mar., 1892-Accepted, 4th June, 1892
PROVISIONAL SPECIFICATION.
Improvements relating to the Manufacture of White-lead and to
Apparatus for use therein.
I, LEON LABOIS, of 95 Boulevard Beaumarchais, Paris, in the Republic of
France, Engineer, do hereby declare the nature of this invention to be as
follows:-
In the manufacture of white-lead by the De Clichy method which consists in
sending a current of carbonic acid through a solution of tribasic acetate of lead the
product obtained is less adapted for coating than that obtained by the Dutch or
similar methods and has therefore less commercial value.
The carbonate precipitated does not present the same appearance whilst the
white-lead produced by the Dutch method is deposited in the form of grainy and
compact powder the white-lead obtained by the De Clichy method is precipitated
in the crystalline state.
It has however been observed that the precipitate obtained at the beginning of
the operation, when the acetate of lead is richest in its base, has the appearance and
the coating power of white-lead obtained by the Dutch method.
According to the improved process which forms the subject of my invention I
treat a basic solution of acetate of lead by carbonic acid, and produce a white-lead
which enables a good coating to be very rapidly obtained with a very small quantity
of material.
The general principle upon which this method is based consists in precipitating
the white-lead from a solution of tribasic acetate of lead in its richest state, and in
discontinuing the precipitation at the precise moment when the liquor is not
sufficiently basic, that is to say, at the moment when the solution ceases to be rich
enough to give a white-lead which coats well.
By thus discontinuing the precipitation just at the moment when the precipitate
would become crystalline, and immediately discharging the liquor therefrom, the
most concentrated mother liquors possible are always obtained and their subsequent
enrichment necessitates only a very small expenditure of labour and heat.
Moreover, and this is one of the new features of my method, this enrichment can
be effected in a closed vessel and even under pressure for enabling these mother
liquors to rapidly digest as much litharge as possible.
Finally my improved method of manufacturing white-lead having as much
coating power as that produced by the Dutch method is based upon the use of both
chemical and mechanical means, these latter having principally the effect of
increasing to the highest degree the rapidity of the manufacture and considerably
diminishing the labour required. It consists in removing after carbonation
preferably effected in a closed vessel, the liquor and its precipitate just at the
moment when the solution ceases to be rich enough to give a white-lead adapted for
coating.
It is evident that the carbonation can be effected under the circumstances stated,
in a closed or open receptacle which may be either fixed or movable, the precipitate
being afterwards treated in any suitable turbine, but in order to dispense with some
operations, useless labour and more or less costly devices which it is difficult to clear,
I preferably employ as a carbonating apparatus a turbine of special construction,
which is hereinafter described.
For carrying my aforesaid process into effect the apparatus which I use comprises
a carbonic acid generator and its adjuncts, such as a gas-holder, purifier, a device
for forcing this gas such as a gas pump a ventilator an injector or the like; a dis-
solving vessel in which the tribasic acetate is constantly reformed, which can be
ת

page_text: effected under pressure in a closed vessel; either a stationary or movable carbonator
which may be the pan of the turbine provided in the turbine or in a special receptacle,
and the turbine such as hereinafter described.
The turbine proper is placed in a wrought iron or cast iron casing having a
removable cover which is adapted to be closed through the medium of thumb
screws, tightness being ensured by a joint of indiarubber or other material. This
casing which forms a receptacle can withstand a pressure of two or more
atmospheres.
An inlet pipe for the steam may be provided either in the axis itself or below the
pan. The carbonic acid, gas may be introduced into the turbine through a tube
traversing the cover. A modification consists in adapting one part of the said tube
to slide in the other.
The aforesaid pan is removable so that it can be rapidly replaced by another
when a sufficient quantity of white-lead has been precipitated. To this end it is
provided with handles for raising the same. It is provided with wire gauze and
with filter cloths of any suitable fabric, such as cotton or asbestos.
Its lower part
may be concave and unperforated whilst its outer part is very oblique so that the
liquor when at rest will fill the lower concavity and rise along the sides during the
rotation.
The operation can be effected in another manner by covering the outer part of
the pan with a cloth pressed by a ring at the desired height and held at the upper
part, in this case the said pan is fixed, and in order to collect the white lead it is
taken at the bottom of the pan and upon the cloth where it has been deposited;
or by arranging in the interior of the first mentioned pan, so as to be fixed to the
axis, an annular crown of wire gauze provided with filtering cloths which then form
the movable pan.
With this turbine the mode of operation is as follows:-
Into the said pan is poured the concentrated tribasic solution, or it is filled
with the desired weight of crystals of tribasic acetate if it is not used in
solution.
The carbonic acid may be caused to enter either through a tube terminating
at the bottom of the pan or through the axis, or else by means of the following
device.
The inlet tube extends through the cover and nearly to the bottom of the pan.
It is pierced with holes for the escape of the gas which is forced either separately
or together with steam.
As the turbine rotates slowly it permits all the parts of the solution to be
successively presented to the tube. This arrangement obviates the great number
of small tubes in use in ordinary carbonating vessels.
When this carbonation is deemed sufficient the joints are made tight the sliding
tube for the distribution is raised or the cover which carries the same is replaced
by another and a rapid movement imparted to the apparatus.
The solution is driven into the exterior receptacle and collected in order to be
enriched again.
Then the turbine is set in motion steam being injected for removing the little
acetate which may be contained in the precipitate. The pan is again charged with
a rich solution, or is changed if the precipitate is sufficient.
Afterwards the white-lead obtained is caused to undergo the ordinary treatment
according to the uses for which it is designed.
In this manner I can obtain supersaturated solutions under pressure by causing
the liquor under pressure to digest an excess of litharge.
Dated this 4th day of June 1891
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements relating to the Manufacture of White-lead and to
Apparatus for use therein.
I, LÉON LABOIS, of 95, Boulevard Beaumarchais, Paris, in the Republic of
France, Civil Engineer, 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:—
In the manufacture of white-lead by the De Clichy method which consists in
sending a current of carbonic acid through a solution of tribasic acetate of lead the
product obtained is less adapted for coating than that obtained by the Dutch or
similar methods and has therefore less commercial value.
The carbonate precipitated does not present the same appearance; whilst the
white-lead produced by the Dutch method is deposited in the form of grainy and
compact powder the white-lead obtained by the De Clichy method is precipitated
in the crystalline state.
It has however been observed that the precipitate obtained at the beginning of
the operation, when the acetate of lead is richest in its base, has the appearance and
the coating power of white-lead obtained by the Dutch method.
According to the improved process which forms the subject of my invention I
treat a tribasic solution of acetate of lead by carbonic acid, and produce a white-
lead which enables a good coating to be very rapidly obtained with a very small
quantity of material.
The general principle upon which this method is based consists in precipitating
the white-lead from a solution of tribasic acetate of lead in its richest state, and in
discontinuing the precipitation at the precise moment when the liquor is not
sufficiently basic, that to say, at the moment when the solution ceases to be rich
enough to give a white-lead which coats well.
By thus discontinuing the precipitation just at the moment when the precipitate
would become crystalline, and immediately discharging the liquor therefrom, the
most concentrated mother liquors possible are always obtained and their subsequent
enrichment necessitates only a very small expenditure of labour and heat.
Moreover, and this is one of the new features of my method this enrichment can
be effected in a closed vessel and even under pressure for enabling these mother
liquors to rapidly digest as much litharge as possible.
Finally my improved method of manufacturing white-lead having as much
coating power as that produced by the Dutch method is based upon the use of both
chemical and mechanical means, these latter having principally the effect of
increasing to the highest degree the rapidity of the manufacture and considerably
diminishing the labour required. It consists in separating after carbonation
preferably effected in a closed vessel, the liquor and its precipitate just at the
moment when the solution ceases to be rich enough to give a white-lead adapted for
coating.
It is evident that the carbonation can be effected under the circumstances stated,
in a closed or open receptacle which may be either fixed or movable, the precipitate
being afterwards taken up again and separated in any suitable turbine, but in order
to dispense with some operations, useless labour and more or less costly devices
which it is difficult to clear, I employ as a carbonating apparatus the turbine of
special construction, which is hereinafter described.
In the accompanying drawing I have shown an apparatus for carrying my afore-
said process into effect.
The improved apparatus comprises a carbonic acid generator and its adjuncts,
such as a gas-holder, purifier; a device for forcing this gas such as a gas-pump, a
ventilator, an injector or the like; a dissolving vessel in which the tribasic acetate
is constantly reformed, which can be effected under pressure in a closed vessel;

page_text: Stationary or movable carbonator, which may be the pan of the turbine
provided in the turbine or in a special receptacle and the turbine such as hereinafter
described.
The turbine proper M is placed in a wrought iron or cast iron casing A having a
removable cover B which is adapted to be closed through the medium of thumb
screws C, tightness being ensured by a joint CC of india-rubber or other
material.
An inlet pipe for the steam may be provided either in the axis of the turbine or
below the pan.
In the accompanying drawing the steam inlet pipe is arranged below the turbine
at V. The carbonic acid gas may be introduced into the turbine through a
tube D E passing through the cover at 4, it descends nearly to the bottom of the
pan and it has at its lower end a series of small holes o through which escapes the
carbonic acid which is slightly forced into the interior of the tube D.
The pan proper G of the turbine which is fixed to the axis P to which a rotary
movement is imparted by means of one of the pullies R R encloses a second pan G¹
provided at its upper part and on its flange with handles H'H'. This arrange-
ment when once the cover B is removed, enables the pan G¹ to be rapidly withdrawn.
When a sufficient quantity of white-lead has been precipitated, that is to say, as
above stated when the liquor is no longer sufficiently basic. Other pans similar to
the pan Gare prepared beforehand so that as one operation is terminated a new
pan can be immediately substituted. The pan G is formed by wire gauze with
filter cloths of any suitable fabric, such as cotton asbestos or the like. The
lower part of the pan G¹ is made of wood or metal. On the side of the turbine is
arranged a tube p provided with a cock which enables, if necessary, the inert gases
to be disengaged.
The pan G being in its place, that is to say, fixed to the axis of the turbine, I
place in the interior thereof the pan G' of gauze or iron wires provided with its
filter cloths, then the cover B and the tubes which it carries is put on the casing A
and the cover is secured by means of nuts C C. The concentrated tribasic solution
is introduced into the pan G¹ through the tube K.
Then a very slow movement is imparted to the turbine so that all the parts of the
solution will successively come in contact with the extremity of the lower tube E
through which the carbonic acid gas passes.
For ensuring the contact of the different parts of the solution with the pipe E
for the inlet of the carbonic acid gas I may provide rakes X which facilitate the
mixing.
When the carbonation is deemed sufficient I close the inlet for the carbonic acid
and raise the tube E so that it is no longer immersed in the solution. A rapid
movement is then imparted to the separator. The solution passes through the
tube L placed at the lower part into a receptacle and is collected in order to be
enriched again.
The little acetate interposed in the precipitate during the operation is removed
by giving a turn to the turbine with injection of steam through the tube L. A
fresh operation may be effected without replacing the pan G₁ by another new pan,
if the precipitate contained in the pan under treatment is not too abundant. By
this process obtain white lead of (great) covering power, which subsequently
undergoes the ordinary manipulations according to the uses to which it is to
be put.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed; I declare that what
I claim is
1. The improved. process of rapidly manufacturing white-leadi which coats well,
consisting in the treatment in a closed vessel, of a tribasic solution of-supersaturated
lead by a current of compressed carbonic acid,. and if necessary of steam; this
carbonation being discontinued before the precipitate, becoming, crystalline, shall

page_text: have lost the qualities of a good white-lead, in combination with an immediate
separation of the mixture, so as to separate the solution at the proper moment, that
is to say at the moment when the precipitate becomes crystalline this process being
if necessary completed for the enrichment, under pressure, of the separated mother
liquors.
2. The employment in the manufacture of white lead of the above described
turbine, in which the operations of the precipitation and immediate separation of the
aforesaid material are effected successively in the pan itself, with the object of
saving labour, cost of construction, and hastening the manufacture.
3. The herein described apparatus for use in the manufacture of white lead
characterized by removable pau, its casing the arrangement of the pan for the
filtering, the mode of tightly closing the same for the separation or carbonation if
necessary in a closed vessel with or without pressure.
Dated this 5th day of March 1892.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.