Improvements in the Manufacture of Lead Pigments or Lead Compounds for Use as Pigmentary Materials.
Year: 1894

page_text: Date of Application, 8th Sept., 1894
Complete Specification Left, 8th July, 1895-Accepted, 7th Dec., 1895
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Lead Pigments or Lead
Compounds for Use as Pigmentary Materials.
I WALTER BISHOP PRIEST of 50 Fenchurch Street, in the City of London,
Gentleman, do hereby declare the nature of my invention to be as follows:-
The object of my invention is to improve and render more economical the
manufacture of lead pigments or lead compounds for use as pigmentary materials.
According to my invention I take sulphate of lead, calcic hydrate and water and
place them in a vessel and apply heat to them. The heat can be applied by steam
or in any other suitable way. prefer to employ the sulphate of lead and calcic
hydrate in relative proportions in accordance with their respective chemical
equivalents or with a slight excess of calcic hydrate.
I prefer to agitate the mixture to facilitate conversion in any suitable way.
A less
Hydrated oxide of lead and calcic sulphate are formed in the reactions.
quantity of calcic hydrate may be used but not less than 14 per cent. relatively to
the sulphate of lead and a mixture of hydrated oxide of lead, sulphate of lead,
and calcic hydrate is thus formed.
After calcic sulphate has been formed I remove it from the mixture. This I
effect by agitating the mixture in a quantity of water not less than will allow of
free movement of the particles of calcic sulphate and hydrated oxide of lead.
This I prefer to do by injecting air at the bottom of the mixture or by causing
steam to pass through it from the bottom upwards so that the mixture is kept
gently agitated from the bottom upwards. The hydrated oxide of lead is thus
gradually freed from the calcic sulphate which is required to be separated therefrom
and the hydrated oxide of lead being the heavier substance falls to the bottom
while the calcic sulphate rises to the surface and can be removed by any convenient
means for example by syphoning or floating it off. Or I remove calcic sulphate
from the mixture by washing it away or dissolving it out; for this purpose a large
proportion of water is required as the calcic sulphate is but slightly soluble or by
this method in addition to the previous method, one or both of these operations may
be performed in the same vessel in which the material is formed or in a separate
vessel after the removal of the material into it. The material when formed should
be well washed and may be dried.
To form white lead or a pigment consisting of white lead and sulphate of lead I
take sulphate of lead, calcic hydrate and water, place them in a vessel and apply
beat to the mixture as hereinbefore described, and I inject into the mixture
carbonic acid gas. This injection may or may not be effected under pressure and
either during or after the application of heat. If effected under pressure the vessel
used will of course be closed and capable of bearing the requisite pressure. The
gas may be passed into the mixture or material after, or before the removal of the
calcic sulphate (which may be allowed to remain in the mixture, but it is preferable
to remove it as it deteriorates the body or covering power and quality of the white
lead) or the gas may be passed over the material when the said mixture or material
is in a dry or moist state & I prefer that the sulphate of lead & calcic hydrate
should be apportioned according to their chemical equivalents. White lead is thus
formed but a less quantity of calcic hydrate may be used and the pigment may
thus be made to consist of a mixture of white lead & sulphate of lead.
The white lead or mixture of white lead and sulphate of lead should be well
washed pressed and dried and inay be ground in oil.

page_text: 5
I also form a pigment by treating the sulphate of lead with not less than
per cent. and not more than 14 per cent. but preferably with between 8 to 11 per cent.
of its weight of calcic hydrate. I place the calcic hydrate and the sulphate of
lead together with water in a vessel capable of being heated by steam or by any
other suitable means. I apply heat to the mixture, the process is expedited by
raising the temperature even up to boiling point but I prefer that the temperature
should not be higher than 190° nor lower than 90° Fahrenheit. I separate calcic
sulphate from the material and remove it as hereinbefore described.
The pigment
is afterwards well washed pressed and dried and may be ground in oil. Or a
pigment may be formed by adding to the sulphate of lead and intimately
incorporating with it (as for instance by grinding them together) the hydrated
oxide of lead or the hydrated oxide of lead and sulphate of lead formed as first
hereinbefore described.
In forming the pigment or piginentary material as above mentioned the reactions
will proceed in the cold but as they proceed very slowly when heat is not applied,
heat should be employed to expedite the process in order to render it practically
available.
The calcic hydrate may be first formed in the same vessel in which the pigment
or pigmentary material is formed as for example by placing calcic oxide in water
in the vessel.
In forming the pigments or pigmentary materials I prefer to use sulphate of lead
made by the process of volatilisation.
Dated this 8th day of September 1894.
JOHNSONS & WILLCOX,
Agents.
Improvements in the Manufacture of Lead Pigments or Lead
Compounds for Use as Pigmentary Materials.
I WALTER BISHOP PRIEST of Gresford North Wales late of 50 Fenchurch
Street, in the City of London Gentleman 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 my invention is to improve and render more economical the
manufacture of lead pigments or lead compounds for use as pigmentary materials.
I place sulphate of lead and calcic hydrate in a vessel with water preferably
first introducing the sulphate of lead and the water and raising the temperature to
a few degrees (say 10°) below boiling point and then adding the calcic hydrate
which should be in the form of an emulsion or magma in water as it is when lime
is slaked or it may be in a dry powdered condition. The mixture may afterwards
be boiled as heat expedites the reactions of the sulphate of lead and calcic hydrate
within the vessel whereby a pigmentary material is formed containing hydrated
oxide of lead and calcic sulphate. The heat may be applied by steam or in any
suitable way.
It should be applied until conversion; which usually takes place
within half an hour and may be ascertained by testing the mixture with test paper
for the presence of calcic hydrate. I prefer to employ the sulphate of lead and
calcic hydrate in relative proportions in accordance with their respective chemical
equivalents and to agitate the mixture to facilitate conversion the quantity of
water used being such as will enable the mixture to be properly agitated.
A pigmentary material is thus produced containing hydrated oxide of lead and
calcic sulphate. A less quantity of calcic hydrate may be employed but preferably
not less than 14 per cent. relatively to the sulphate of lead when a pigmentary
material will be formed containing hydrated oxide of lead sulphate of lead and

page_text: 1
:
calcic sulphate. The pigmentary material so formed may be dried. The tempera-
ture of the drying process should be low say 150° Fahrenheit. Or sulphate of
lead may be added to the pigmentary material produced as aforesaid or to the .
pigmentary material obtained by the removal of calcic sulphate as hereinafter
mentioned. And I prefer that the weight of the sulphate of lead added should be
so apportioned that the weight of the calcic hydrate should be 8 to 11 per cent. of
the entire weight of the sulphate of lead which is treated and which is added as
aforesaid. The pigmentary material may be mixed with the sulphate of lead in
the vessel or mixed or ground with it when the material has been removed from
the vessel and when it is in the wet or moist state or after it has been dried but if
in the wet or moist state the pigment should be afterwards dried at a low
temperature as before mentioned and may be mixed or ground in oil. Or a
pigment may be formed without the addition of a further quantity of sulphate of,
lead by placing sulphate of lead and calcic hydrate in a vessel with water and
treating the materials as before described but apportioning the quantity of calcic.
hydrate so that its weight shall be not more than 14 per cent. but preferably 8 to
11 per cent. of the weight of the sulphate of lead treated. Not less than 5 per cent.
should be employed. The. pigment so formed should be dried and may be mixed .
or ground in oil.
But I prefer to manufacture or produce white lead or a pigment containing
white lead and sulphate of lead by treating the sulphate of lead with calcic
hydrate in any desired proportions and injecting carbonic acid gas as hereinafter
described.
I effect the removal of calcic sulphate from the mixture (when such removal is
desired) by agitating it in a quantity of water sufficient to allow of the free
movement of the particles of calcic sulphate and hydrated oxide of lead and of the
subsequent separation of the hydrated oxide of lead from the calcic sulphate. The
agitation may be effected by causing steam to pass through the mixture from
the bottom upwards; which may be done by boiling the mixture. By this upward
agitation the hydrated oxide of lead becomes separated from the calcic sulphate
which is required to be separated therefrom and the hydrated oxide of lead, when,
the mixture is allowed to stand, falls to the bottom, the calcic sulphate being above,
and the latter can be removed by any convenient means as by drawing it off through
an aperture in the side of the vessel in which the reactions have been conducted or.
to which it may have been removed. Or the agitation may be effected mechanically.
preferably by a vertical agitator.
To form white lead or a pigment containing white lead and sulphate of lead.
I take sulphate of lead and calcic hydrate (which should be in the condition.
aforesaid) and place them in a vessel with water preferably raising the temperature
of the mixture before the calcic hydrate is added, to a few degrees (say 10°) below
boiling point and then adding the calcic hydrate and afterwards boiling the mixture
to expedite conversion and preferably agitating it, the quantity of water used
being such as will enable the mixture to be well agitated as before mentioned and
I inject into the mixture carbonic acid gas preferably not until the mixture has
been kept at boiling temperature for half an hour or until conversion of the calcic
hydrate which may be ascertained by test paper as before mentioned. The injection
of the gas may or may not be effected while the gas is under pressure and either
during or after the application of heat. But if injected as above described the gas
is rapidly absorbed and hydrated carbonate of lead or white lead is produced in a
few minutes. The gas may if desired be passed over the material formed by
treating sulphate of lead with calcic hydrate when the material is in the dried or
moist state as by passing the gas into a vessel or chamber in which the material is
contained. I prefer that the sulphate of lead and calcic hydrate should be
apportioned according to their respective chemical equivalents but a less quantity
of calcic hydrate may be used and the pigment may be made to contain white lead
and sulphate of lead together with some calcic sulphate which is left after the
reactions.
:
;

page_text: Calcic sulphate may if required be reduced in quantity or removed from the
mixture as before mentioned but without its removal the material is of good quality
owing to the smallness of the quantity of calcic sulphate and its intimate association
with the white lead or white lead and sulphate of lead. The gas may be injected
into the vessel or be passed over the material when in the dry or moist state after
the separation or reduction in the quantity of the calcic sulphate.
The white lead or white lead and sulphate of lead should be well washed pressed
and dried at a moderate temperature and may be ground in oil.
In forming the pigment or pigmentary material whether resulting from the
treatment of sulphate of lead with calcic hydrate alone or with calcic hydrate and
carbonic acid gas as above described the reactions proceed in the cold but I prefer
instead of so conducting the reactions to apply heat to expedite the process by
which I form the pigment or pigmentary material.
If it be desired to dispense with heat the mixture of sulphate of lead calcic
bydrate and water should be made in the form of a thin emulsion and be well
agitated until conversion which can be ascertained as herein before mentioned.
The calcic hydrate may be first formed in the same vessel in which the pigment
or pigmentary material is formed as by placing calcic oxide in water in the vessel
and then converting it into the hydrate or slaked lime.
The carbonic acid gas and the calcic oxide may be obtained for the above
mentioned purposes from limestone or chalk or other carbonate of lime as in the
manufacture of the oxide or quicklime.
In forming the pigment or pigmentary materials I prefer to use the sulphate of
lead formed by the process of volatilisation. The sulphate of lead produced as a
bye-product in manufacturing processes may also be employed.
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 manufacture of lead pigments or lead compounds for use as pigmentary
materials from sulphate of lead and calcic hydrate substantially in the manners
hereinbefore described.
2. The manufacture of lead pigments or lead compounds for use as pigmentary
materials from sulphate of lead and calcic hydrate with the application of heat and
agitation substantially as hereinbefore described..
3. The manufacture of lead pigments or lead compounds for use as pigmentary
materials from sulphate of lead and calcic hydrate and then separating calcic
sulphate substantially as herein before described.
4. The manufacture of white lead or a pigment containing white lead and sulphate
of lead in either of the following ways:
(a) By causing sulphate of lead and calcic hydrate to react and then passing
carbonic acid gas into the resulting products either in water or in the dry
state substantially as hereinbefore described.
(6) By causing sulphate of lead and calcic hydrate to react and carbonic acid
gas to act as aforesaid with the application of heat and agitation in water
substantially as hereinbefore described.
(c) By causing sulphate of lead and calcic hydrate to react as aforesaid and
after the separation of calcic sulphate subjecting the resulting product to
the action of carbonic acid gas whether the said product be in water or in
a moist or dry state substantially as hereinbefore described.
י
1
CL
1005
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.