A METHOD OF MAKING WHITE LEAD DIFFERENT FROM THE METHODS NOW PRACTISED OR USED, AND WITHOUT THE AID OF HORSE LITTER, OR TANNER'S BARK, OR BOTH OF THEM
Year: 1804

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SAXELBYE'S SPECIFICATION.
TO ALL TO WHOM THESE PRESENTS, SHALL COME, I, JOHN,
SWIFT SAXELBYE, of the Town of Derby, in the County of Derby, White Lead,
Maker, send greeting.
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WHEREAS His most Excellent Majesty George. the Third, by, the
grace of God of the United Kingdom of Great Britain and Ireland King,,
Defender, of the Faith, by His Letters. Patent under the Great Seal of the,
United Kingdom of Great Britain and Ireland, bearing date at. Westminster,
on or about the Fourteenth day of May, in the forty-fourth year of His said;
Majesty's reign, did, give and, grant unto me, the said John Swift Saxelbye,
my exors, admors, and assigns, His special licence, full power, sole privilege-
and authority, that I, the said John.Swift Saxelbye, my exors, admors, and
assigns, and every of them, by myself and themselves, or by my and their,
deputy or deputies, servants or agents, or such others as I, the said John
Swift Saxelbye, my exors,.adñors, or assigns, should at any time agree with,
and no others, from time to time and at all times thereafter during. the term.of
years therein expressed, should and lawfully might make, use, exercise,, and,
vend my Invention of "A METHOD OF MAKING WHITE LEAD DIFFERENT FROM THE
METHODS NOW PRACTISED OR USED, AND WITHOUT THE AID OF HORSE LITTER, OR
TANNER'S BARK, OR BOTH OF THEM," within that part of the United Kingdom of
Great Britain and Ireland called England, the Dominion of Wales, and Town
of Berwick-upon-Tweed, in such manner as to me, the said John Swift
Saxelbye, my exors, adñors, or assigns, or any of them, should in my or their
discretions seem meet; in which said Letters Patent there is contained a
proviso that if I, the said John Swift Saxelbye, should not particularly describe
and ascertain the nature of my said Invention, and in what manner the

page_text: same was to be performed, by an instrument in writing under my hand and
seal, and cause the same to be inrolled in His Majesty's High Court of
Chancery within one calendar month next and immediately after the date of
the said Letters Patent, that then the said Letters Patent, and all liberties
and advantages whatsoever thereby granted, should utterly cease, determine,
and become void, as by reference to the said Letters Patent will more fully
appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
John Swift Saxelby, do hereby declare that my said Invention is described
in manner following (that is to say):-
Instead of applying heat or causing an increase of temperature (in the pots
or vessels containing the acid, and the metallic lead intended to be subjected
to the process by which white lead is made) by means of horse litter or
tanner's bark, or both of them, or by means of the gradual decomposition
or change which takes place during the decay and rotting of those or any
other remains of organized bodies, I do avail myself of and make use of
that augmentation of temperature or sensible heat which is produced and
communicated by the combustion of fuel, and I do regulate and manage
the said heat so that the same shall be kept within the proper limits, and
shall be sufficient to cause the intended change or oxidation of the lead in
an effectual manner without causing the acid in the pots to be volatelized to a
greater degree than is necessary for the intended purpose, and the particular
means by which I do perform the same are described as follows:-I make
my fire or fires in a proper stove or receptacle, with its apertures, flues,
chimneys, registers, dampers, and other parts which require no particular
description, because it will be sufficient if the construction thereof be such as
that the operator or attendant shall have it in his power to manage and
regulate the fire and the communication of heat in the usual manner. The
said stove is so built or placed as to communicate heat as generally and
uniformly as may be to a room or space constructed of such materials and.
dimensions as to receive the pots containing the usual charge of metallic
lead and acid, and to admit of the same being regularly placed and disposed
and shut up, but that none of the smoke, vapours, or other immediate exhala-
tions from the fuel should be admitted within the said room or space. And I
do not only cause the quantity of heat to be regulated by an attention to the
quantity or weight, and the nature or kind of the fuel to be consumed in any
determinate time, but I do still more completely enable my operator to keep
the temperature at the requisite degree, by introducing or inserting. one or
more thermometers into the room.or space_containing the pots, but having

page_text: their scales or graduations so placed as to indicate any changes of heat that may
take place in the said room or space; and the said thermometers may be of
any proper and fit construction, according to the well-known methods wherein
mercury or any other fluid is used, or wherein all the parts are solid, as in the
instruments called pyrometers. And moreover, and for the purpose of pre-
venting any wasteful or pernicious excess of heat, I do construct and make at
some convenient place in the upper part of the said room or space a valve, or
shut, or aperture, capable of being opened to let out some of the heated air or
elastic fluid when the same is requisite to be done; and I do connect with the
cover or lid or stopper of the said valve, either the arm of a float, supported
by the mercury of a large thermometer, or else the arm of a pyrometrical
apparatus or expansion bar, so that, by an action which every mechanical
man acquainted with subjects of this nature will readily apprehend, the increase
of temperature shall cause the said valve to be opened, and contrarywise,
diminution of temperature shall suffer the same to be again closed. And I do
find by experience that the temperatures best calculated for these operations
are, that the said room or space should be kept between ninety and one
hundred degrees of Fahrenheit's scale during the first ten or twelve days, and
from one hundred to one hundred and ten for the next eight days, and that
the heat be regularly and equally increased about ten degrees for each
successive portion of eight days, until the expiration of about six weeks in
the whole from the commencement of the operation, or until the vinegar
or other acid liquor shall have been evaporated, at which period the
pots are to be taken out and the white lead seperated and ground for sale,
as usual. Lastly, I do in some cases make use of water or steam as
the medium of communication through or by which the heat, so as afore-
said produced, is transmitted into the said room or space containing the said
pots; and in these last-mentioned cases the said water or steam may be
still further and usefully employed for general purposes that constitute no part
of my said Invention, though the economy of the said Invention may be
thereby in such cases promoted; and I do then, if needful, make thermo-
metrical observations on the temperature of the said water or steam, in order
the better to regulate and govern my fire, and the general process of my said
Invention dependant thereon.
In witness whereof, I have hereunto set my hand and seal, this Six-
teenth day of May, in the forty-fourth year aforesaid, and in the year
of our Lord One thousand eight hundred and four.
JN° SWIFT (L.S.) SAXELBYE.

page_text: AND BE IT REMEMBERED; that on the Seventeenth day of May, in the
year of our Lord 1804, the aforesaid John Swift Saxelbye came before our said
Lord the King in His Chancery, and acknowledged the Specification afore-
said, and all and every thing therein contained and specified, in form above.
written. And also the Specification aforesaid was stampt according to the
tenor of the Statutes made for that purpose.
Inrolled the Seventeenth day of May, in the year of our Lord One
thousand eight hundred and four..