A New or Improved Process for Producing Minium.
Year: 1890

page_text: · Date of Application, 1st July, 1890-Accepted, 2nd Aug., 1890
COMPLETE SPECIFICATION.
A New or Improved Process for Producing Minium.
I, MEINHARD ALSBERG, of 169 East 116th Street, New York in the County of New
York and State of New York, in the United States of America, 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:-
Heretofore minium in its commercial forms of red lead or orange mineral has been
manufactured by exposing oxide of lead (litharge) or hydro-carbonate of lead (white
lead) for a long time to air at a temperature between 500° and 600° F. The monoxide
of lead (i.e. litharge or oxide resulting from the decomposition of the carbonate) absorbs
oxygen, forming a tripiumbic tetroxide or plumbic plumbate which possesses a more
or less red colour. According to the state of fineness of the material employed the
oxidation is more or loss complete and it is almost impossible to so control the
absorption of oxygen as to have the whole of the material converted into triplumbic
tetroxide.
The object of my invention is to provide better and more certain means of oxidation
and to reduce the time and labor required for the same. To this end my invention
consists in incorporating nitrate of lead into the material employed, which may be
either oxide or carbonate of lead, and exposing the mixture to a moderate heat,
sufficiently high to decompose the nitrate of lead and by the oxygen of the nitric acid
convert the lead monoxide into the triplumbic tetroxide (or plumbic plumbate), but not
high enough to decompose this latter and reconvert it into the monoxide. The nitrate
of lead by its decomposition supplies oxygen for the convertion of the plumbic mon-
oxide into triplumbic tetroxide without leaving any foreign substance which might
either combine with the lead oxide or have to be removed by lixiviation.
In carrying out my invention, I mix dilute nitric acid with either litharge or
white lead, thereby obtaining a mixture of basic lead nitrate with lead oxide or lead
carbonate.
This mixture I expose to a heat of about 700 to 900 degrees Fahrenheit. The
reaction i.e. the decomposition of nitrate of lead and the formation of minium takes
place at about the melting point of zinc, which is 775-5° Faht. or at an incipient red
heat. Care must be taken not to heat up to a red heat, at which minium is decomposed
and fusion takes place. The process may be carried on by placing the material upon
the hearth of a reverberatory furnace, or of a muffle, or the mass may be packed into
iron or clay trays or pots. By the application of heat any water that may be contained
in the mass is first evaporated and, when the temperature rises to about the melting
point of zinc the lead nitrate is decomposed and supplies oxygen for the formation of
minium. Access of air or stirring the mass are not absolutely necessary when a
sufficient quantity of nitric acid has been used, but when the mass is heated in a muffle
or on the hearth of a reverberatory furnace it should be stirred from time to time.
In place of incorporating nitrate of lead into the material by forming it within the
same as above described, nitrate of lead already formed may be incorporated into the
material, either dry, or preferably, as an aqueous solution which latter insures a more
intimate mixture.
In practice I use for 100 parts by weight of litharge about 7.1 parts of hydrogen
nitrate (i.e. nitric acid) diluted with sufficient water to make about 12.5 parts. Or I
take for 100 parts of litharge 18-6 parts of lead nitrate and 15 parts of water.
case of white lead I take a quantity containing 100 parts of lead oxide.
In the
My invention however is not restricted to the above mentioned proportions. I have
obtained a good colour by heating a mixture of 100 parts of litharge and 5 parts of
lead nitrate giving the air free access to the mass, whereas the same kind of litharge
without the addition of lead nitrate, exposed to the same degree of heat for the same
D

page_text: length of time, did not change its colour materially. Likewise a larger quantity of
lead nitrate may be employed provided care be taken to decompose the nitrate com-
pletely.
For the finest quality of orange mineral I use by preference litharge produced by
burning atomized lead, or lead carbonate precipitated from a basic lead acetate solution
by carbonic acid (so-called French process white lead).
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
The within described process of producing minium which consists in incorporating
lead nitrate into the material (oxide or carbonate of lead) and exposing the resulting
mixture to heat sufficiently high to first drive off any water that may be contained
in it, and then to decompose the lead nitrate, thereby furnishing oxygen for the
formation of minium.
DL1 1 1000
MEINHARD ALSBERG.
By Harris & Mills,
23, Southampton Buildings, London, Agents.