IMPROVEMENTS IN THE CONDENSATION OF METALLIC FUMES, AND IN THE MANUFACTURE OF WHITE LEAD
Year: 1848

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
RICHARDSON, of Newcastle-upon-Tyne, Chemist, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of the United Kingdom of
Great Britain and Ireland, bearing date at Westminster, the Twenty-first
day of August, One thousand eight hundred and forty-eight, in the twelfth
year of Her reign, did, for Herself, Her heirs and successors, give and grant
unto me, the said Thomas Richardson, my exors, adñiors, and assigns, Her
especial licence, full power, sole privilege and authority, that I, the said
Thomas Richardson, my exors, adñiors, and assigns, and such others as I,
the said Thomas Richardson, my exors, adñiors, or assigns, should at any
time agree with, and no others, from time to time and at all times during
the term of years therein expressed, should and lawfully might make, use,
exercise, and vend, within England, Wales, and the Town of Berwick-upon-
Tweed, my Invention of "IMPROVEMENTS IN THE CONDENSATION OF METALLIC
FUMES, AND IN THE MANUFACTURE OF WHITE LEAD;" in which said Letters
Patent is contained a proviso that I, the said Thomas Richardson, should
cause a particular description of the nature of my said Invention, and the
manner in which the same is to be performed, by an instrument in writing
under my hand and seal, to be inrolled in Her said Majesty's High Court of
Chancery within six calendar months next and immediately after the date
of the said in part recited Letters Patent, as in and by the same, reference
being thereunto had, will more fully and at large appear.

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
Thomas Richardson, do hereby declare that the nature of my said Invention,
and the manner in which the same is to be performed, are fully described and
ascertained in and by the following statement thereof, reference being had to
the Drawing hereunto annexed, and to the figures and letters marked thereon,
that is to say:-
The first part of my Invention consists in preparing a certain description of
lead for the manufacture of white lead, and in treating this lead so prepared,
or other suitable lead, in a particular manner for the production of white lead.
I expose what is known in trade as tea lead in a melted state to a slow
current of hot air in an ordinary red lead furnace, or in an iron pan encased in
brickwork similar to that already in use in calcining hard lead. The tin
contained in the tea lead is oxidized by this means, and floats on the surface,
mixed with a small variable quantity of oxide of lead, and the workman
removes the oxide thus formed, by means of an iron rake, from time to time.
The process is known to be complete by the melted lead becoming sufficiently
soft to be easily scratched by the finger nail, and when this point is reached
the whole of the remaining lead is drawn out of the furnace in the usual
manner, and cast into suitable moulds. The tea lead thus treated is remark-
ably pure, and fit for conversion into white lead by any of the methods already
in use, or by that which I shall now proceed to describe.
In explaining the nature of this part of my Invention, I shall describe, first,
the materials and their preparation; second, the apparatus; and, lastly, the
process itself.
First, materials and their preparation. I use lead in the metallic form in a
fine state of division, either as crystals which are produced in the desilverising
process of Pattinson, or as granulated lead mado in the ordinary way, and
acetic or nitric acids as they usually occur in commerce, either mixed or alone,
diluted with their own bulk of water, or a solution of acetate or nitrate of
lead, either alone or mixed, containing the same amount of real acetic or
nitric acids, with steam, hot air, and carbonic acid. The air is heated by
forcing it, by means of a fan, blast, or other suitable machinery, through a
series of pipes exposed to the action of fire in a stove, in a manner similar to
that practised in the smelting of iron. The carbonic acid may be obtained
from the burning of limestone, coke, or charcoal, or any of the sources known
to chemists. The apparatus a, a, a, is a strong framing of wood or stone, or
other suitable material, divided into five shelves 1, 2, 3, 4, 5, each with a
bottom b, b, b, b, b, and a top c, c, c, c, c, with two or three inches space
between d, d, d, d, d. The small uprights e, e, e, e, e, serve to support the

page_text: shelves and to form a recess, in which the doors f. ff, rest when the whole is
closed. The shelves may be constructed of wood, lined with sheet lead, or of
stone or slate flags, I prefer the latter as more durable. The spaces d, d, and
the sides 7, 9, are made close by stone or wood. The front and back h, h, are
similarly constructed. Steam and carbonic acid gas are admitted by means of
pipes into each of the chambers i, i, i, i, i, as illustrated in the sketch at l, k,
which respectively shew a gas and steam pipe; hot air is admitted in a similar
manner into each of the spaces d, as illustrated by the pipe l. The chain-
bers i are about nine inches high, about seven or eight feet square, and from
twenty to thirty hundredweight of the finely divided metallic lead is evenly
spread over their surface, as shewn by m, m. For the convenience of working,
the breadth ought not to exceed seven or eight fect, but it is easy to perceive
that the length may be extended at pleasure, according to the quantity it is
proposed to make. When steam is employed in the place of hot air the
spaces d must be made steam-tight, with an exit pipe for condensed water.
The process consists in moistening a loose mass of finely divided metallic lead
from time to time, with acetic acid or any other of the solutions, as previously
explained, in the proportion of about two or three gallons of ordinary com-
mercial acetic acid to twenty hundredweight of lead, and turning such mass
over a few times; twenty to thirty hundredweight of lead so prepared is thrown
into each chamber and spread equally over the surface by means of a wooden
rake. The carbonic acid is then admitted, and allowed to remain in contact
with the lead until it is converted into crude white lead.
At the same
the hot air or steam, as the case may be, is forced into the space d, until the
bottom is brought to a temperature of about ninety or one hundred degrees,
at which heat it ought to be maintained as steadily as possible during the
period of conversion. The constant admission of hot air or steam would, of
course, soon raise the temperature beyond this point; and the workman must
use his judgment as to when and how long this heating operation ought to be
carried on, which a little practise soon enables him to regulate. In like
manner the steam is occasionally admitted into the chamber to maintain the
artificial atmosphere of carbonic acid gas in a moist state, but never to such
an extent as to do more than render the lead damp to the touch. When this
degree of moisture is exceeded the process of conversion is delayed, or when
the bottom heat is allowed to fall so as to cause the steam to condense to too
great an extent, the same effect is produced. In either case the workman
must encrease the heat of the space d, to restore the lead to its proper degreo
of moisture. When all the conditions are properly attended to, the conversion
of the lead will be completed in about ten or fourteen days. The degree of

page_text: conversion is easily ascertained from time to time by pounding a little of the
lead in a mortar with water, which leaves the metallic lead at the bottom of
When the
the vessel after the suspended white lead has been poured off.
conversion is deemed complete, the crude white lead is removed to some
convenient locality, from whence it is taken to be ground under a pair of
ordinary edge stones and washed in a dolly tub of the usual construction.
By this means any minute particles of metallic lead are separated, and remain
at the bottom of the dolly, whence they are removed to the shelves along with
a fresh portion of original lead. The white lead which floats away from the
dolly is collected in a subsiding vessel or cistern, and finally ground between a
pair of horizontal stones, washed and dried, as is practised in white lead
manufactories on the old plan.
The second part of my Invention relates to the condensation of metallic
vapors or fumes, which I effect in the following manner:-I force steam
into the main flue, with which the various furnaces employed in treating
different metallic substances are connected, through a small iron pipe opening
into such flue, at a distance of one or two feet in advance of each furnace.
Each iron pipe is provided with a stopcock, but it is immaterial whether each
furnace is at work so long as the steam issuing into the main flue is in advance
of the last furnace actually in operation, and sufficient steam is admitted as
not to interfere with the draught of the furnace while the condensation of the
metallic fume is effected. At or near to the chimney with which the main
flue is in connection I erect a tower, at least twenty feet high, divided into
two compartments by a division wall which reaches to within a certain
distance of the top of the tower. The capacity of each division of the tower,
and the passage between them and the top of the partition wall is made a
little larger than the capacity of the main flue in connection with it. Midway
in the descending division of this tower I fix a number of iron bars, upon
which I lay a quantity of hard burnt coke or broken bricks, &c., in pieces
about the size of small paving stones. The top of this tower is pierced with
small holes, about a quarter of an inch diameter, through which a continual
supply of water is kept running, which falling upon the coke, &c., is scattered
on all sides, and is thus brought into contact with the metallic fumes already
in a damp state, by the partial condensation of the steam admitted into the
main flue. The depth of the layer of coke or broken bricks, &c. depends
upon the power of the draught of the chimney and the efficiency of the
condensation. If the chimney has power to draw through a layer of coke
sufficient to condense the metallic fumes, I employ no other incans of draught
but should the depth of the layer of coke, &c. necessary for condensation execc

page_text: the power of the chimney to draw through, I place one or more jets of steam,
as described in Mr. Watson's Patent, in the flue between the tower and the
chimney, to ensure sufficient draught to effect the condensation through the
medium of the steam and water falling upon the coke.
I claim,-
First, the separation of tin and other impurities from tea lead by means of
oxidation through the use of hot air.
Second, the use of carbonic acid, acetic or nitric acids, alone or mixed,
free or combined with oxide of lead, steam, and hot air, for the conversion
of metallic lead into white lead.
Third, the use of steam in conjunction with a shower of water, and with or
without a steam jet, for condensing metallic fumes.
In witness whereof, I, the said Thomas Richardson, have hereunto set
my hand and seal, this Fifteenth day of February, in the year of our
Lord One thousand eight hundred and forty-nine.
THOMAS (L.S.) RICHARDSON.
Signed, sealed, and delivered, by the
said Thomas Richardson (being first
duly stamped), in the presence of
AND BE IT REMEMBERED, that on the Fifteenth day of February,
in the year of our Lord 1849, the aforesaid Thomas Richardson came before
our said Lady the Queen in Her Chancery, and acknowledged the Specification
aforesaid, and all and every thing therein contained and specified, in form
above written. And also the Specification aforesaid was stamped, according
to the tenor of the Statute made for that purpose.
Enrolled the Twenty-first day of February, in the year of our Lord
One thousand eight hundred and forty-nine.