IMPROVEMENTS IN THE MANUFACTURE OF OXIDE OF LEAD
Year: 1882

page_text: LETTERS PATENT to Henry Harris Lake, of the Firm of Haseltine, Lake,
& Co., Patent Agents, Southampton Buildings, London, for an Invention of
"IMPROVEMENTS IN THE MANUFACTURE OF OXIDE OF LEAD." A communi-
cation from abroad by George T. Lewis, of Philadelphia, Pennsylvania,
United States of America.
COMPLETE SPECIFICATION filed by the said Henry Harris Lake at the
Office of the Commissioners of Patents on the 15th May 1882.
HENRY HARRIS LAKE of the Firm of Haseltine Lake & Co., Patent Agents
Southampton Buildings London. "IMPROVEMENTS IN THE MANUFACTURE OF
OXIDE OF LEAD." A communication from abroad by George T. Lewis, of
Philadelphia, Pennsylvania, United States of America.
Heretofore commercial oxides of lead have been manufactured by heating
metallic lead in an oxidizing, reverberatory, or revolving furnace, or by heating
carbonate of lead or white lead in such furnaces to drive out carbonic acid and
combined water.
The present Invention is based on a discovery that commercial oxides of lead
may be manufactured more economically from lead fumes, such as are produced by
totally or partially subliming and oxidizing galena ore or other lead ore, or from
waste lead fumes from lead smelting or roasting furnaces or from complex lead and
zinc ores.
The fumes produced by subliming and oxidizing galena ore may contain merely
sulphate, sulphite, and oxide of lead with more or less arsenic and antimony; waste
lead fumes from lead sinelting furnaces generally contain more or less sulphide of
lead; and complex lead and zinc fumes contain a large quantity of oxide of zinc.
According to the said Invention I subject lead fumes in the manner hereinafter
described to the joint action of carbonate of soda or caustic soda and heat by
roasting, and bleaching powder chloride of lime or chloride of soda may be added
when the fumes contain sulphide or sulphuret of lead, and I dissolve the zinc out
of complex lead and zinc fumes by the use of sulphuric acid.

page_text: The process may be carried on by intimately mixing lead fumes with carbonate
of soda or caustic soda and roasting the mixture in an ordinary litharge furnace or
other reverberatory or muffie furnace for several hours when the charge must be
drawn and washed with water to separate the insoluble oxide of lead from the
soluble sulphate and sulphite of soda and arsenic and antimony soda compounds.
By this process, the sulphate and sulphite of lead are changed into carbonate of
lead or hydroxide of lead, and arsenic and antimony are converted into soluble
compounds.
By the roasting process the compounds of lead are converted into oxide of lead,
the color and composition of which depend upon the length of time during which
the roasting is continued.
In this method of employing the said process, it is not necessary to add any
chloride of lime or chloride of soda to react upon the sulphide of lead which may
be contained in the fumes, since by the roasting the sulphide of lead will be
partially oxidized into sulphate of lead and partially into oxide of lead and the
sulphate of lead again converted into oxide of lead by the action of heat, and
carbonate of soda or hydrated soda. However, this method has the disadvantage
that the decomposition will be complete, only when the mixing of the fumes with
the carbonate of soda is performed with the greatest care.
I therefore prefer the following method. The lead fumes, in a pulpy state, are
boiled in, a solution of carbonate of soda or caustic soda for from thirty to sixty
minutes and for a longer time if the fumes contain much arsenic. By this boiling
the sulphate and sulphite of lead are changed into carbonate or hydrated oxide of
lead while arsenic and antimony are dissolved. The solution is then allowed to
settle and after it is well settled the liquor is drawn off. The pulp is carefully
washed in water, either by decantation or in a filter press or pressure filter to
remove the sulphate of soda, and is then placed in a furnace and roasted for several
hours when it becomes litharge, and by longer roasting, red lead, or orange mineral.
When the fumes are the product of complex lead and zinc ores, the zinc
contained in the fumes must be removed by the action of sulphuric acid, before
the last described method is employed. By this means the zinc is rendered soluble
and is removed by washing as sulphate of zinc. When the fumes contain sulphide
of lend, they may also be boiled in a solution of chloride of lime or chloride of
soda in the first instance, or chloride of soda may be mixed with the carbonate of
soda employed in the method described. The liquor, after boiling with carbonate
of soda is mainly sulphate of soda with some sulphite of soda and soda compounds
of arsenic and antimony. This may be boiled down after removing the arsenic
and antimony and will yield a salt, which can be used in glass making and for
other commercial purposes.
The relative proportions required for the successful operation of the methods
ahove described are determined by the character and composition of the lead
fumes. To each 151 parts of sulphate of lead and to each 143 parts of sulphite
of lead are required 53 parts of carbonate of soda or 40 parts of hydrated soda.
Practically, I prefer to use an excess of five per cent or 55-56 parts of carbonate of
soda.
To dissolve each 99 parts of arsenious acid, 53 parts of carbonate of soda will be
found quite sufficient. And for each 119 parts of sulphide of lead, chloride of
lime or chloride of soda equivalent to 106 parts of chloride and 53 parts of
carbonate of soda may be used. Thus if the lead fumes are composed of 0.57 per
cent carbon, 61-30 per cent sulphate of lead, 28.07 per cent oxide of lead, 3.79
per cent sulphuret of lead, and 5.37 per cent arsenious acid, there will be required,
in one hundred parts of the fumes, 3 parts of chloride and 27 parts of carbonate
of soda.
Having thus fully described the said Invention as communicated to me by my
foreign correspondent and the manner of performing the same I wish it understood
that I claim,
First. The process of manufacturing commercial oxides of lead by subjecting

page_text: lead fumes to the joint action of carbonate of soda or caustic soda and heat by
roasting in a furnace, substantially as set forth.
Second. The process of manufacturing commercial oxides of lead, by subjecting
lead fumes to the action of carbonate of soda or caustic soda, by boiling them
together and afterwards heating the resulting carbonate of lead or hydrated oxide
of lead in a furnace, substantially as set forth.
Third, The purification of lead fumes containing sulphuret of lead by the
addition of bleaching powder before or during the boiling with carbonate of soda
or caustic soda, substantially as set forth.
Fourth. The process of manufacturing commercial oxides of lead, by subjecting
fumes from complex lead and zinc ores to the action of sulphuric acid, removing the
zinc thus made soluble, and then boiling the insoluble sulphate of lead with a
solution of carbonate of soda or caustic soda and roasting the resulting carbonate
of lead or hydrated oxide of lead in a furnace, substantially as set forth.
In witness whereof I the said Henry Harris Lake have hereunto set my
hand and seal this Fifteenth day of May in the year of our Lord One
thousand eight hundred and eighty two.
TOYOT