and Compounds and in Apparatus therefor.
Year: 1886

page_text: and Compounds and in Apparatus therefor.
J JAMES BALLANTYNE HANNAY of Cove Castle Loch Long in the County of
Dumbarton, North Britain Chemist, do hereby declare the nature of this Invention to
be as follows, that is to say :-
My said Invention has principally for its object the manufacture of a pure or
nearly pure amorphous sulphate of lead by treating lead compounds such as ores,
slags, waste or impure sulphate, or the like in an improved manner hereinafter
described, in order to obtain the said sulphate in a condition to form a good white
pigment, and sufficiently pure for the preparation of various lead salts or compounds.
In carrying out the Invention the ores or other lead compounds are treated in a
furnace which is by preference of an improved construction, and when the compounds
contain less sulphur than what is required to form all the lead into sulphate sulphur
must be added in the form of iron pyrites or other suitable form. The present process
is distinguished from certain previously tried processes in avoiding the formation of
sulphite or its presence in the final product.
The first stage of the process or the furnacing is conducted as usual with coke and
a suitable flux in a furnace the lower part of which is of a vertical form with a lead
well for running off reduced lead, also with slag hole and tuyeres as in an ordinary
vertical smelting furnace, a hot blast being by preference used. The upper part of
the furnace diverges to one side into a reverberatory chamber in which the fume
formed below may roll or circulate so as to become thoroughly oxidised and the
presence of sulphite avoided. The reverberatory chamber may if necessary be heated
by an auxiliary fire; or there may be substituted for the chamber one or more
externally heated tubes. The oxidation is effected by air suitably admitted or by
means of nitre in a pot placed in the reverberatory chamber or in any suitable part
of the flue, any free or combined sulphurous acid present being converted into
sulphuric acid in the same manner as in the ordinary manufacture of sulphuric acid.
Or nitrous vapour or other suitable oxidising agent may be passed into the chamber
or flue from an external source. In some cases the completion of the oxidation of

page_text: the lead compounds may be deferred to a later stage after the fume has been
condensed but it is by preference effected in the reverberatory chamber or flue as
described.
In the second stage the fume or sublimate with the gases accompanying it is passed
through condensing and collecting apparatus which is by preference of an improved
kind described in my Provisional Specification accompanying another Application for
Letters Patent to bear the same date as the present.
If sulphuric acid is not present so as to become dissolved in the water of the
condenser some may be added to convert any oxide or sulphite of lead into sulphate
and to dissolve any zinc, iron, or other impurities which may accompany the fume.
In the third stage the crude lead sulphate is transferred from the condenser to a
suitable vessel and any acid water is run off from it; and if it is found to be
sufficiently pure it may be washed and dried as hereinafter described. If however
the lead sulphate is found when delicately tested to show any grayish tint, this will
indicate the presence of a trace of insufficiently oxidised compound. To remove
this the white lead is treated with nitric acid, or aqua regia, or chlorine, or acidified
hypochlorite, or chlorite, or chlorate or other suitable oxidising agent. Aqua regia
appears to be preferable as it will dissolve out colored impurities as well as oxidise
any lead compound. The lead sulphate is allowed to lie until the proper whiteness is
attained and is then washed first with water afterwards with water containing alkali
to remove the last traces of acid, and finally with water again and then dried.
The product thus obtained is of a very pure whiteness inclining neither to blue nor
to cream color; and if a sharp faintly bluish white is desired it may be mixed with
oxide of zinc, the mixture having body and covering power imparted to it by the
lead and beauty of tint by the zinc.
The sulphate of lead obtained by the process hereinbefore described is well adapted
for preparing other salts or compounds of lead, it being in a very fine (nearly
molecular) state of division. Treated by boiling with excess of an alkaline carbonate
it yields a pure carbonate of lead, from which other salts or compounds can be
prepared in well known ways. Or the sulphate may be treated with excess of an
alkaline chromate or bichromate to form chromate of lead. Treated with a sulphide
of an alkali the sulphate of lead yields sulphide of lead in a powder which is so fine
that it is desirable to mix with it some suitable inert substance on account of the
facility with which it oxidises and its consequent liability to enter into combustion.
The chromate and sulphide of lead may be obtained in a very pure state from the
carbonate formed as herein before described.
L 11
, ז
1

page_text: and Compounds and in Apparatus therefor.
I, JAMES BALLANTYNE HANNAY, of Cove Castle, Loch Long in the County of
Dumbarton, North Britain, 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 :-
My said Invention has principally for its object the manufacture of a pure or
nearly pure amorphous sulphate of lead by treating lead compounds such as ores,
slags, waste or impure sulphate, or the like in an improved manner hereinafter
described, in order to obtain the said sulphate in a condition to form a good white
pigment, and sufficiently pure for the preparation of various lead salts or compounds.
In carrying out my Invention the ores or other lead compounds are treated in a
furnace which is by preference of an improved construction, and when the compounds
contain less sulphur than what is required to form all the lead into sulphate, sulphur
must be added in the form of iron pyrites or other suitable form. The present process
is distinguished from certain previously tried processes in avoiding the formation of
sulphite or its presence in the final product.
The first stage of the process or the furnacing is conducted as usual with coke and
a suitable flux in a furnace the lower part of which is of a vertical form with a lead
well for running off reduced lead, also with slag hole and tuyeres as in an ordinary
vertical smelting furnace a hot blast being by preference used. The upper part of
the furnace diverges to one side into a reverberatory chamber in which the fume
formed below may roll or circulate so as to become thoroughly oxidised and the
presence of sulphite avoided. The reverberatory chamber may if necessary be heated
by an auxiliary fire; or there may be substituted for the chamber one or more
externally heated tubes. The oxidation is effected by air suitably admitted or by
means of nitre in a pot, placed in the reverberatory chamber or in any suitable part
of the flue, any free or combined sulphurous acid present being converted into
sulphuric acid in the same manner as in the ordinary manufacture of sulphuric acid.
Or nitrous vapour or other suitable oxidising agent may be passed into the chamber
or flue from an external source. In some cases the completion of the oxidation of
the lead compounds may be deferred to a later stage after the fume has been
condensed, but it is by preference effected in the reverberatory chamber or flue as
described.
In the second stage the fume or sublimate with the gases accompanying it is passed
through condensing and collecting apparatus which is by preference of an improved
kind described in the Complete Specification relative to my Application for Letters
Patent bearing the same date as the present one and numbered 16290 of 1886.
If sulphuric acid is not present so as to become dissolved in the water of the
condenser some may be added to convert any oxide or sulphite of lead into sulphate
and to dissolve any zinc, iron, or other impurities which may accompany the fume.

page_text: In the third stage the crude lead sulphate is transferred from the condenser to a
suitable vessel and any acid water is run off from it; and if it is found to be
sufficiently pure it may be washed and dried as hereinafter described. If however
the lead sulphate is found when delicately tested, to show any grayish tint, this will
indicate the presence of a trace of insufficiently oxidised compound. To remove
this the lead sulphate is treated with nitric acid, or aqua regia, or chlorine, or acidified
hypochlorite, or chlorite, or chlorate or other suitable oxidising agent. Aqua regia
appears to be preferable as it will dissolve out colored impurities as well as oxidise
any lead compound. The lead sulphate is allowed to lie until the proper whiteness is
attained and is then washed first with water, afterwards with water containing alkali
to remove the last traces of acid, and finally with water again, and then dried.
The product thus obtained is of a very pure whiteness inclining neither to blue nor
to cream color; and if a sharp faintly bluish white is desired it may be mixed with
oxide of zinc the mixture having body and covering power imparted to it by the
lead sulphate and beauty of tint by the zinc.
The sulphate of lead obtained by the process herein before described is well adapted
for preparing other salts or compounds of lead, it being in a very fine (nearly
molecular) state of division. Treated by boiling with excess of an alkaline carbonate
it yields a pure carbonate of load, from which other salts or compounds can be
prepared in well known ways. Or the sulphate may be treated with excess of an
alkaline chromate or bichromate to form chromate of lead. Treated with a sulphide
of an alkali the sulphate of lead yields sulphide of lead in a powder which is so fine
that it is desirable to mix with it some suitable inert substance on account of the
facility with which it oxidises and its consequent liability to enter into combustion.
The chromate and sulphide of lead may be obtained in a very pure state from the
carbonate formed as hereinbefore described.
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 combination of processes substantially such as are hereinbefore
described for the manufacture of lead sulphate to be used as a white pigment or
for making other lead compounds or pigments.
2. The improved furnace for manufacturing lead sulphate and comprising a lower
vertical part in which the materials are first heated and an upper lateral reverberatory
chamber in which the oxidation is further effected substantially as and for the
purposes hereinbefore described.
3. The employment of processes or operations substantially such as are herinbefore
described for completing the oxidation of the lead sulphate and separating impurities.
Dated this Fourteenth day of July 1887.
EDMUND HUNT,
Applicant's Agent.