IMPROVEMENTS IN THE MANUFACTURE OF LEAD PEROXIDE ALSO APPLICABLE TO THE PRODUCTION OF OTHER METALLIC PEROXIDES
Year: 1882

page_text: LETTERS PATENT to Farnham Maxwell Lyte of the Science Club, Savile Row
in the County of Middlesex for an invention of IMPROVEMENTS IN THE
MANUFACTURE OF LEAD PEROXIDE ALSO APPLICABLE TO THE PRODUCTION OF
OTHER METALLIC PEROXIDES
PROVISIONAL SPECIFICATION left by the said Farnham Maxwell Lyte at
the Office of the Commissioners of Patents on the 12th April 1882.
FARNHAM MAXWELL LYTE, of the Science Club, Savile Row in the County of
Middlesex "IMPROVEMENTS IN THE MANUFACTURE OF LEAD PEROXIDE ALSO
APPLICABLE TO THE PRODUCTION OF OTHER METALLIC PEROXIDES
"
One of the modes of manufacturing lead peroxide Pb O given in chemical
works is that of adding bleaching powder to a soluble salt of lead; no particular
proportions are however usually stated. Now if bleaching powder be added to a
salt of lead, say for instance to a solution of lead chloride in the cold, the peroxide
is but slowly formed, a precipitate first of all going down of a pale yellow or
brownish yellow tint, and this only slowly changes to the brown peroxide. If the
liquor be heated the peroxide forms at once, but there is produced in the cold
solution some free hydrochloric acid at the same time, and this reacting on the lead
peroxide formed or on any free bleach which may be present, gives rise to a strong
evolution of chlorine as soon as heat is applied, the stifling fumes of which would
entirely preclude any possibility of working on a large scale, not to mention the
loss occasioned thereby.
{OH
In describing the reaction by which I manufacture lead peroxide, we will adopt
OCI
the formulæ 2 Ca + CaCl2 + 2 (H2O) as representing the composition of
the best bleaching powder, and discarding the Ca Cl, which takes no direct
part in the reaction, the action of bleach upon lead chloride may be represented by
the following equation—

page_text: back again with generation of 2 equivalents of free chlorine. Were clear bleach
liquor to be employed in place of the powder, the evolution of chlorine would be
doubled with production of proportionately less of the hydrated plumbic oxido as
is shown in the following equation :—
Ca (OC) +2 Pb Cl³ + 4 (H2O) = 2 PыO (OH) + Ca Cl³ + 4 HCI
The proportionate quantity of hydrated plumbic oxide formed is here the same,
but as the proportionate quantity of HCI is doubled, ono half instead of one
quarter of it tends to revert back to the condition of Pb Cl or in other words is
not formed at all and Cl in double the quantity is generated. If however we
take the bleach liquor and add to it two equivalents of dry slaked lime 2 Ca (OH)"
for each equivalent of Ca (OCI)³ prosont, wo can with such a solution decompose
2 equivalents of lead chloride with formation of 2 equivalents of hydrated plumbic
oxide and 3 of calcium chloride.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Farnham Maxwell Lyte at the Great Seal Patent Office
on the 12th October 1882.
FARNHAM MAXWELL LYTE of the Science Club, Savile Row in the County of
Middiosex IMPROVEMENTS IN THE MANUFACTURE OF LEAD PEROXIDE, ALSO
APPLICABLE TO THE PRODUCTION OF OTHER METALLIC PEROXIDES."
My Invention relates to the manufacture of metallic peroxido and especially
peroxide of lead, from soluble salts of the metals, and in the case of lead especially
from chloride of lead.
Metallic peroxides have been manufactured previously by the addition of
chlorine to solutions of the soluble metallic salts, but I manufacture the peroxides
by using a solution or cream of bleaching powder to which has been added some
quick limo or hydrate of lime so as to prevent the hydrochloric acid which is also
formed during the reaction from attacking the peroxide after it is made and the
liberation of free chlorine.
It is essential in carrying the Invention into practice, that the soluble metallic
salt should always be in excess, and that the solution of the bleach should be
added to the metallic solution and not the metallic solution to the bleach. I will
describe the Invention as applied to the manufacture of peroxide of lead, and will
describe two different modes of carrying it into effect.
The bleaching powder which is to be used is first accurately titrated to ascertain
the amount of available chlorine which it contains, and the slaked lime which
is to be used is also assayed to ascertain the proportion of hydrate of lime which
it contains.
The bleaching powder and lime are then mixed in the proportion of two
equivalents of the bleaching powder to one equivalent of the slaked lime and tho
substances mixed with water into a thick or strong cream which must be carefully
separated from lumps or gritty particles. The quantities of bleach and lime used
may be such that each gallon of water shall contain about 3 to 3'/, lbs of the raw
materials, i.c. of the mixture of bleach and lime. I prepare another solution of
chloride of lead, but as chloride of lead is very slightly soluble oven in boiling
water, I prefer to proceed as follows:-I take a suitable tub or vessel, the contents
of which can be heated by steam or otherwise, and I put into it chloride of lead
in the proportion of two equivalents of chloride of lead for every two equivalents
of bleaching powder which I have used, I then add boiling water of about four
times the weight of the chloride of lead to bo used. This quantity of water will
be insufficient to dissolve the whole of the chloride of lead at once, but some
portion will dissolve and the remainder will forin a magma with the solution.
I then add the cream of bleach and lime very slowly to the boiling solution of
chloride of lead, stirring thoroughly during the whole time. The addition of the
bleach solution causes the deposition of peroxide of lead, by decomposing the
chloride of lead which is in solution, and the liquor which remains immediately
dissolves a further quantity of the chloride of lead which was previously undissolved,
so that the action goes on continuously until all the chloride of lend has been
decomposed and converted into peroxide. The precipitate which will then settle
out from the liquor, will necessarily contain the insoluble impuritics of the bleach
and of the chloride of lead, and it will therefore be desirable to select samples of
bleach, chloride of lead, and lime, which are of good quality. The peroxide which
settles may be thrown onto a filter, washed with water or diluto nitric acid so as
to free it as far as possible from substances which are soluble in nitric acid and

page_text: water, and from the chloride of calcium which is formed in the mother liquora
during the reaction. Working in this way it will be found that about 1 lb peroxide
of lead can be made for every one gallon capacity of the tank or tub in which the
precipitation takes place.
In many cases I find an advantage in adding chloride of sodium (common salt)
to tho chloride of lead in order to increase its solubility. I find that chloride of
sodium equal to /, the weight of the chloride of lead to bo used, is a very suitable
proportion. When this is done it is possible to make about 1%, lb of peroxide of
lead for each gallon of capacity of the operating tub. It is sometimes desirable
to make the peroxide of lead of greater purity and quite free from any insoluble
substances which may be contained in the bleaching powder. In this case I proceed
as follows make a saturated solution of bleaching powder and allow the
insoluble matter to settle and decant the clear liquor which I test to find the
proportion of available chlorine which it contains. I then inix this solution with
good freshly slaked hydrate of lime in the proportion of 1 equivalent of hydrate of
lime to 1 equivalent of chlorine.
I make the magma of chloride of lead solution exactly as in the previous process,
and I add this solution of bleaching powder and cream of lime very slowly to tho
solution of lead, with constant agitation, taking care that the chloride of lead
always remains in excess, even when the operation is completed.
It is evident that by this mode of treatment the insoluble impurities of the
blench will be kept out and the resulting peroxide of load will be more pure.
In this case however I prefer, as in the last, to transfer the precipitate to a
filter and wash it with water or dilute nitric acid,
It is obvious that chlorides of sodium may be used to assist the solubility of the
chloride of lead in this case as in the other.
When using this process it is not possible to make so much peroxide per gallon
of liquor operated upon, and it will be found in practice that 1 lb of peroxide for
every two gallons of capacity of the operating tub, will be about the best result
which can be obtained.
In manufacturing other metallic peroxides, I prepare the solution of bleach and
lime precisely as directed in this specification for the preparation of peroxido
of lead, and I add the bleaching solution to the metallic salt in the same relative
proportion according to the chemical equivalents of the metal being treated.
Having described the nature of the Invention and the manner of performing the
same, I declare that what I claim as my Invention to be protected by the herein-
before in part recited Letters Patent is.
The manufacture of metallic peroxides and especially the manufacture of
peroxide of lead essentially as described.
In Witness whereof I the said Farnham Maxwell Lyte have hereunto set
iny hand and seal this ninth day of October, A.D. 1882.
Witness
C. M. LYTE.
41 Coleman St
London, E.C.
F MAXWELL-LYTE (L.S.)