IMPROVEMENTS IN UTIL IZING CERTAIN COMPOUNDS PRODUCED IN THE PROCESS OF GALVANIZING IRON, AND IN THE APPLICATION OF THE SAME AND SIMILAR COMPOUNDS TO CERTAIN USEFUL PURPOSES
Year: 1855

page_text: LETTERS PATENT to William Hunt, of Tipton, in the County of Stafford,
Manufacturing Chemist, for the Invention of "IMPROVEMENTS IN UTIL
IZING CERTAIN COMPOUNDS PRODUCED IN THE PROCESS OF GALVANIZING IRON,
AND IN THE APPLICATION OF THE SAME AND SIMILAR COMPOUNDS TO CERTAIN
USEFUL PURPOSES."
Sealed the 27th April 1855, and dated the 3rd March 1855.
PROVISIONAL SPECIFICATION left by the said William Hunt at the
Office of the Commissioners of Patents, with his Petition, on the 3rd
March 1855.
I, WILLIAM HUNT, of Tipton, in the County of Stafford, Manufacturing
Chemist, do hereby declare the nature of the Invention for "IMPROVEMENTS
IN UTILIZING CERTAIN COMPOUNDS PRODUCED IN THE PROCESS OF GALVANIZING IRON,
AND IN THE APPLICATION OF THE SAME AND SILILAR COMPOUNDS TO CERTAIN USEFUL
PURPOSES," to be as follows:-
That my improvements may be well understood, I shall first describe the
ordinary mode of coating iron with zinc. An iron pot being set in brickwork,
with a fire placed under it and flues, the pot is filled with the metal zinc; a
fire is put under the pot to melt the metal, which being melted and heated

page_text: to the proper temperature, sal-ammoniac is thrown over the surface of the
metal, which operates as a flux, covering the surface of the metal, to
prevent oxidation as much as possible, and also to facilitate the coating or
galvanizing of the iron which is dipped into the melted metal. The iron,
previous to being dipped in the melted metal, is prepared by first steeping it
in dilute sulphuric or muriatic acid, and sometimes both; sometimes the
iron is washed in water after being thus steeped and dried in an oven, the
iron is then ready for dipping. The sal-ammoniac is added to the metal
from time to time on account of its volatilizing by the heat of the melted
metal, but a considerable portion of the sal-ammoniac is decomposed by the
metallic zinc, making chloride of zinc; this effects a considerable loss of
zinc. The chloride of zinc is skimmed off from time to time as refuse with
some oxide of zinc which forms on the surface of the metal.
Having described the ordinary mode of, and articles used in, coating iron
with zinc, I wish it understood that I propose to employ chloride of zinc as
a flux, instead of using sal-ammoniac, or chloride of zinc with a little sal-
ammoniac may be used, my object being to substitute chloride of zinc for
sal-ammoniac to avoid the loss of zinc which now occurs by the use of sal-
ammoniac, and further, because chloride of zinc can be obtained much cheaper.
This chloride of zinc being skimmed off occasionally will be a proper sub-
stance to be used as a flux again (after it has been dissolved from the
oxide of zinc), but it must be first boiled until all or nearly all the water is
evaporated from it. When the chloride of zinc has been washed from the
oxide, the oxide may be used for making metallic zinc in the usual way, or it
may be used for other purposes. In the event of the oxide being contaminated
with chloride of zinc, I add caustic lime to decompose it and wash out the
muriate of lime. I also wish it to be understood that I propose to steep
the iron (to be coated) in a solution of chloride of zinc, then dry it before
dipping into the melted metal.
When the iron to be coated is steeped in dilute sulphuric acid, sulphate of
iron is formed to a considerable extent, but the solution containing this is
thrown away as useless even when it contains a considerable quantity of free
sulphuric acid. I recover the uncombined acid and the sulphuric acid combined
with the iron in doing this: I boil the liquor to a concentrated state in a lead
pan or other suitable apparatus, then I transfer it to a close furnace where
the temperature is sufficient to distil over the free sulphuric acid, and
ultimately the sulphuric acid is roasted off from the iron; in this latter case a
little air is admitted into the furnace. I collect the sulphuric acid by sending
the acid fumes into a condenser filled with pebbles, and a little water is added

page_text: from time to time to assist the condensation. The sulphuric acid thus obtained
may be used again for cleansing iron.
The essence of my Invention consists in using chloride of zinc in place of
sal-ammoniac in coating iron with zinc or other metals, and recovering the
sulphuric acid which has been used in cleaning the iron; also the use of a
solution of chloride of zinc for washing the iron in after cleaning and previous
to coating.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Hunt in the Great Seal Patent Office on the
3rd September 1855.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
HUNT, of Tipton, in the County of Stafford, Manufacturing Chemist, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Third day of March, in the year of our Lord
One thousand eight hundred and fifty-five, in the eighteenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said William IIunt, Her special licence that I, the said William Hunt,
my exccutors, administrators, and assigns, or such others as I, the said William
Hunt, my executors, administrators, and assigns, should at any time agree
with, and no others, from time to time and at all times thereafter during the
term therein expressed, should and lawfully might make, use, exercise, and
vend, within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN UTILIZING CERTAIN
COMPOUNDS PRODUCED IN THE PROCESS OF GALVANIZING IRON, AND IN THE APPLICATION
OF THE SAME AND SIMILAR COMPOUNDS TO CERTAIN USEFUL PURPOSES," upon the
condition (amongst others) that I, the said William Hunt, by an instrument
in writing under my hand and seal, should particularly describe and ascertain
the nature of the said Invention, and in what manner the same was to be
performed, and cause the same to be filed in the Great Seal Patent Office
within six calendar months next and immediately after the date of the said
Letters Patent.
NOW KNOW YE, that I, the said William Hunt, do hereby declare the
nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement thereof (that is to say):-
In order that my Invention may be the better understood, I will describe

page_text: the ordinary mode of coating iron with zinc-An iron pot is set in brickwork,
with a fire-place under it and flues round it. The pot is filled with the metal
zinc. A fire is put under the pot to melt the metal. After it has been melted
and heated to the proper temperature, sal-ammoniac is thrown over the
surface of the metal, which sal-ammoniac operates as a flux, covering the
surface of the metal, and preventing oxidation to a great extent; it also
facilitates the coating or galvanizing of the iron which is dipped into the
melted metal. The iron, previous to being dipped into the melted metal, is
prepared or cleaned by first steeping it in dilute sulphuric acid, by which the
oxide on the surface is removed. After being thus steeped in sulphuric acid
it is steeped in muriatic acid, then removed to an oven to be dried; the iron is
then ready for dipping in the pot containing the melted zinc. Sal-ammoniac is
added to the metal from time to time, on account of its volatilizing by the heat
of the melted metal; but a considerable portion of the sal-ammoniac is
decomposed by the metallic zinc, chloride of zinc being formed. A considerable
loss of zinc is thus occasioned, the chloride of zinc being removed from the
surface of the metal from time to time as refuse, together with some oxide of
zinc, which also forms on the surface of the metal.
Having described the ordinary mode of, and articles used in, coating iron
with zinc, I proceed to describe my Invention; namely, I employ chloride of
zinc as a flux instead of sal-ammoniac, or a mixture of chloride of zinc with a
little sal-ammoniac may be used; my object in substituting chloride of zinc
for sal-ammoniac being to avoid the loss of zinc which occurs in the ordinary
process, by the use of sal-ammoniac, and also because chloride of zinc can be
obtained at a much lower cost than sal-ammoniac.
I also use a solution of chloride of zinc, instead of muriatic acid to steep the
iron in before it is put into the pot to be galvanized, the object being to carry
a coating of chloride of zinc on the articles when they are immersed in the
melted zinc, instead of a coating of chloride of iron, as in the ordinary process,
the latter being objectionable on account of the iron of the chloride of iron
entering into combination with the melted zinc, and falling to the bottom of
the pot as an alloy, which effects a considerable loss of zinc.
I will now describe the mode of carrying that part of my Invention into
effect which relates to the use of chloride of zinc as a flux instead of or as a
substitute for sal-ammoniac. I take two casks or vats which I fill with the
mixture chloride of zinc and oxide of zinc that has been removed as refuse
from the surface of the melted zinc; I put hot water on the said mixture in
the vats to dissolve out the chloride of zinc; the solution is drawn off and
replaced with hot water from time to time until all or nearly all the chloride

page_text: of zinc is dissolved and separated from the oxide of zinc; I then remove the
oxide from the vats and put in fresh refuse, to be operated upon with hot
water in the way described. Where it is wished to make the oxide into chloridé
of zinc, instead of removing the said oxide of zinc from the yats, I add muriatic
acid thereto, which dissolves the oxide of zinc, and the solution of chloride of
zinc formed is drawn off as wanteḍ. I place one vat above the level of the
other, so as to be able to run the solution of chloride of zinc from the top vat
through the bottom one, so as to exhaust the top one first, then the residuum
is removed from the bottom vat to the top vat, and the bottom one is recharged.
The solutions of chloride of zinc so obtained are evaporated in an iron pot
until all or nearly all the water is driven off; the chloride of zinc is then in
a fit state to be used in the galvanizing pot on the surface of the melted zinc
as a flux instead of sal-ammoniac. The chloride of zinc on the surface of the
melted zinc will thicken eventually by some oxide of zinc which is formed.
This mixture of chloride and oxide of zinc is removed from time to time, and
is a fit article to be subjected to the vat process before described to yield a
supply of chloride of zinc.
Having thus described the mode of carrying out that part of my Invention
which relates to the use of chloride of zinc as a flux, I will proceed to describe
that part of my Invention which relates to the use of chloride of zinc for
steeping iron in before it is galvanized instead of muriatic acid. In doing this,
I use a cast-iron vessel, which I call the steeping pot; the shape or dimensions
of this pot may be varied, according to the size of the articles required to be
steeped therein. I set this steeping pot in brickwork, with a fire-place under
or round it; I put into it a solution of chloride of zinc, which I raise to a
boiling heat, and I prefer to keep the solution of such a density as is indicated
by 70 or 80 degrees of Twaddell's hydrometer. The articles to be galvanized,
having been previously steeped in dilute sulphuric acid and cleaned, are put
into the hot solution of chloride of zinc, from whence they are taken to be
galvanized. The articles when taken out of the solution of chloride of zinc
are so hot that all or nearly all the moisture is driven from them before they
are immersed in the melted zinc. If the solution of chloride of zinc is not
sufficiently hot to cause the articles taken from it to dry before they are
immersed in the melted metal, there will be slight explosions on immersing
the moist articles in the zinc bath.
Having now described the nature of my said Invention, and the manner in
which the same is to be performed, I wish it to be understood that I do not
limit myself to the precise details herein described, as the same may be varied
without departing from the nature of my said Invention; but I claim as my

page_text: Invention, the use of chloride of zinc in place of sal-ammoniac in coating iron
with zinc, and in the use of a solution of chloride of zinc for steeping the
iron in after cleaning, and previous to being galvanized, as herein described.
In witness whereof, I, the said William Hunt, have hereunto set my
hand and seal, this First day of September, in the year of our Lord
One thousand eight hundred and fifty-five.
Witness,
GEORGE SHAW.
WILLIAM HUNT. (L.S.)