Improvements in or relating to the Manufacture of Litharge and Red-lead.
Year: 1890

page_text: Date of Application, 10th Mar., 1890
Complete Specification Left, 6th Dec.; 1890-Accepted, 31st Jan., 1891
PROVISIONAL SPECIFICATION.
Improvements in or relating to the Manufacture of Litharge and
Red-lead.
I, GEORGES LARROUY of St. André Pez Lille, (Nord), in the Republic of
France, Engineer, do hereby declare the nature of this invention to be as
follows
The method of producing red-lead most generally employed at the present day is
that of manufacturing it in reverberatory furnaces.
These furnaces are of various types, but the manner of treatment adopted in them
is usually as follows:-
A certain quantity of lead in pigs is introduced into the furnace and placed on
the hearth; when the lead has attained a red heat, a workman stirs the fused mass
in such a way has constantly to expose fresh surfaces to oxidation, at the same time
pushing back the oxide formed to the end of the hearth to prevent clogging and
impeding of the action. When apparently all the lead has been oxidized the oxide
is spread out evenly over the hearth and the workman traces a number of furrows
up and down through the mass in order to oxidize any particles of lead that may
have escaped the action of the air. The firing has to be conducted with the greatest
care, as it is absolutely necessary to avoid fusion of the oxide. When it is con-
sidered that the oxidation is sufficiently complete the fire is extinguished and the
working-door of the furnace fastened up; whereupon the mass is permitted to
remain undisturbed for 24 hours.
The oxide thus obtained which is known by the name of litharge (massicot) is a
yellowish green substance containing small particles of non-oxidized lead distributed
through it which must be got rid of.
On cooling the litharge aggregates into large hard blocks.
The apparatus for crushing and washing the litharge consists of a large vessel
the cover of which is a thick cast-iron slab or plate on which turn a pair of vertical
rolls set in motion by a central shaft to the portion of which below the slab are
attached fans or plates. These fans are designed to effect the suspension in the
water contained in the vessel of the powdered litharge which falls into it. The
water bearing the finer portions of the litharge in suspension runs out of the vessel
by an overflow and falls in cascade into a series of five basins where it deposits the
suspended litharge. It finally enters a cistern from which it is withdrawn by a
pump to be used over again which can be done as often as desired. The
litharge thus freed from metallic particles is placed in rectangularly cast-iron boxes
and introduced into a reverberatory furnace situated above.the oxidizing furnace and
heated by the waste heat therefrom. It is important not to raise the temperature
above 320° and the litharge is kept at this temperature for 72 hours.
At the end of this time it is removed and the operation of sampling is cominenced,.
that is to say specimens are taken from each box and examined: those boxes in
which it is found that the litharge is sufficiently converted into red-lead are passed,
the others being replaced in the furnace where they are kept for 144 hours.
The red-lead in the boxes passed is finely powdered and packed in cases.
Struck by the inconveniences of this method and by the length of time required
by the various operations involved, I have endeavoured to discover a means of
remedying them. The result of my researches has been to lead me to employ a
muffle-furnace suited to the purpose in view and hereinafter described.
Description. I heat my furnaces by means of superheated steam, and I attain by
this novel application of superheated steam the manufacture of red-lead, either by
converting litharge into red-lead, or by converting lead into red-lead directly.

page_text: To attain this last result it is necessary to reduce the lead to an impalpable
powder by any suitable means. In the state of powder, lead is easily oxidisable and
can be transformed into red-lead with rapidity.
To accomplish this conversion of litharge or of powdered lead into red-lead, or
of powdered lead into litharge only, I employ an apparatus the arrangement of
which is apparent from the accompanying drawing in which
Fig. 1 shows the apparatus in vertical section.
Fig. 2 is a horizontal section through the line 12.
etc.,
ai is a cast iron case furnished with supports for the drawers or shelves
and with the movable drawers or shelves g. A jacket r surrounds this case, and
is kept filled with superheated steam at a suitable temperature by means of heaters
unconnected with the case. The case itself is placed in the flue leading from the
heaters, the waste gases passing along which help to maintain its temperature.
is the grate.
d, is the heater for the steam, which is superheated and conducted by the pipe.e
into the jacket or casing which it enters at h. The outlet of the steam is at k.
The smoke and gases from the grate traverse the flues i and pass out at j.
The heat from the grate e superheats the steam in the heater and in the jacket.
The litharge or powdered lead is placed on or in the shelves or drawers, where it
is subjected for a period of from 12 to 15 hours to the action of the heat communicated
to the case aby contact conduction and radiation from the superheated steam
jacket. At the expiration of this time the drawers are removed and found to contain
the red-lead as finished product.
The temperature of the jacket and of the case is maintained constantly at a
suitable point, and the oxidation of the lead or litharge takes place with certainty,
and without danger to the workmen, and without appreciable expense, as the con-
sumption of fuel is insignificant. The steam permits the passage of heat through it
without difficulty and gives up its heat with facility.
My process presents the following advantages:-
1st. The regular and certain manufacture of red-lead by means of superheated
steam the temperature of 300-320 degrees being obtainable with mathematical
precision and easily maintained.
2nd. Considerable economy of fuel as the steam requires only very little coal to
superheat it, and in this condition gives up very easily the heat it contains.
3rd. Saving of time, as, by my process litharge and red-lead may be manufactured
in at most a quarter of the time required by the methods hitherto known.
Dated this 10th day of March 1890.
W. P. THOMPSON & BOULI
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in or relating to the Manufacture of Litharge and
Red-lead.
1, GEORGES LARROUY of St. Andre Pez Lille (Nord), in the Republic of
France, 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:-
The method of producing red-lead most generally employed at the present day
is that of manufacturing it in reverberatory furnaces.
These furnaces are of various types, but the manner of treatment adopted in
them is usually as follows:-
A certain quantity of lead in pigs is introduced into the furnace and placed on
the hearth when the lead has attained a red heat, a workman stirs the fused mass
in such a way as constantly to expose fresh surfaces to oxidation, at the same time
pushing back the oxide formed to the end of the hearth to prevent clogging and
impeding of the action. When apparently all the lead has been oxidised the oxide

page_text: is spread out evenly over the hearth and the workman traces a number of furrows
up and down through the mass in order to oxidize any particles of lead that may
have escaped the action of the air. The firing has to be conducted with the
greatest care, as it is absolutely necessary to avoid fusion of the oxide. When it is
considered that the oxidation is sufficiently complete the fire is extinguished and
the working-door of the furnace fastened up; whereupon the mass is permitted to
remain undisturbed for 24 hours.
The oxide thus obtained which is known by the name of litharge (massicot) is a
yellowish green substance containing small particles of non-oxidized lead distributed
through it which must be got rid of
On cooling the litharge aggregates into large hard blocks.
The apparatus for crushing and washing the litharge consists of a large vessel
the cover of which is a thick cast-iron slab or plate on which turn a pair of vertical
rolls set in motion by a central shaft to the portion of which below the slab are
attached fans or plates. These fans are designed to effect the suspension in the
water contained in the vessel of the powdered litharge which falls into it. The
water bearing the finer portions of the litharge in suspension runs out of the vessel
by an overflow and falls in cascade into a series of five basins where it deposits the
suspended litharge. It finally enters a cistern from which it is withdrawn by a
pump to be used over again which can be done as often as desired. The litharge
thus freed from metallic particles is placed in rectangular cast-iron boxes and
introduced into a reverberatory furnace situated above the oxidising furnace and
heated by the waste heat therefrom. It is important not to raise the temperature
above 320° C. and the litharge is kept at this temperature for 72 hours.
At the end of this time it is removed and the operation of sampling is commenced,
that is to say specimens are taken from each box and examined; those boxes in
which it is found that the litharge is sufficiently converted into red-lead are passed,
the others being replaced in the furnace where they are kept for 144 hours.
The red-lead in, the boxes passed is finely powdered and packed in cases.
Struck by the inconveniences of this method and by the length of time required
by the various operations involved, I have endeavoured to discover a means of
remedying them. The result of my researches has been to lead me to employ a
muffle-furnace suited to the purpose in view and hereinafter described.
Description. I heat my furnaces by means of superhcated steam, and I attain by
this novel application of superheated steam the manufacture of red-lead, either by
converting litharge into red-lead, or by converting lead into red-lead directly.
To attain this last result it is necessary to reduce the lead to an impalpable
powder by any suitable means. In the state of powder, lead is easily oxidisable
and can be transformed into red-lead with rapidity.
To accomplish this conversion of litharge or of powdered lead into red-lead, or of
powdered lead into litharge only, I employ an apparatus the arrangement of which
is apparent from the accompanying drawings in which
Fig. 1 shows the apparatns in vertical section.
Fig. 2 is a horizontal section through the line 12 of Fig. 1.
ab is a cast iron case furnished with supports for the movable drawers or
shelves g. A jacket surrounds this case, and is kept filled with superheated
steam at a suitable temperature by means of heaters unconnected with the case.
The case itself is placed in the flue i leading from the heaters, the waste gases
passing along which help to maintain its temperature.
is the grate.
dis the heater for the steam, which is superheated and conducted by the pipe e
nto the jacket or casinge which it enters at h. The outlet of the steam is at k.
The smoke and gases from the grate traverse the flues i and pass out at j.
The heat from the grate e superheats the steam in the heater d and in the jacket .c.
The litharge or powdered lead is placed on or in the shelves or drawers Y: where it
s subjected for a period of from 12 to 15 hours to the action of the heat com-
nunicated to the case a b by contact conduction and radiation from the superheated

page_text: steam jacket. At the expiration of this time the drawers are removed and found to
contain the red-lead as a finished product.
The temperature of the jacket and of the case is maintained constantly at a suitable
point, and the oxidation of the lead or litharge takes place with certainty, and
without danger to the workmen, and without appreciable expense, as the consumption
of fuel is insignificant. The steam permits the passage of heat through it without
difficulty and gives up its heat with facility.
My process presents the following advantages :-
1st. The regular and certain manufacture of red-lead by means of superheated
steam the temperature of 300-320 degrees C. being obtainable with precision and
easily maintained.
2nd. Considerable economy of fuel as the steam requires only very little coal to
superheat it, and in this condition gives up very easily the heat it contains.
3rd. Saving of time as by my process litharge and red-lead may be manufactured
in at most a quarter of the time required by the methods hitherto known.
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 -
1. The application of superheated steam to the manufacture of litharge and red-
lead from lead in pigs or powder and also to the manufacture of red-lead from
litharge whatever its origin substantially as described.
2. The apparatus substantially as herein described and illustrated in the accompany-
ing drawings for the application of the superheated steam which both by contact and
radiation is to heat the litharge or powder of lead for the required space of time
such litharre or lead being placed upon movable shelves or drawers arranged in a
case-surrounded by the superheated steam.
Dated this 6th day of December 1890,
W. P. THOMPSON & BOULI,
Agents for the Applicant.