IMPROVEMENTS IN OBTAINING USEPUL PRODUCTS FROM CERTAIN MATERIALS PRODUCED IN THE PROCESS OF GALVANISING OR COATING IRON WITH ZINC
Year: 1866

page_text: PROVISIONAL SPECIFICATION left by Charles Crockford at the Office
of the Commissioners of Patents, with his Petition, on the 27th November
1866.
I, CHARLES CROCKFORD, of Holywell, in the County of Flint, Gentleman,
do hereby declare the nature of the said Invention for "IMPROVEMENTS IN
OBTAINING USEPUL PRODUCTS FROM CERTAIN MATERIALS PRODUCED IN THE PROCESS
OF GALVANISING OR COATING IRON WITH ZINC," to be as follows:-
The first part of my Invention consists in the mode of treating the material
known as bath or flux skimmings, and I proceed as follows: I boil first the
material in one or two waters, and drain the liquor therefrom, and then I'
grind it in a wet state and submit the resulting paste-like mass to pressure,
whereby. I am enabled practically to obtain the whole of the soluble salts
which it contains, sometimes I omit the boiling as a treatment preliminary to
the grinding. I then proceed to treat the expressed liquor in one of the
following ways:-1. I precipitate the zine with milk of lime, taking care to
add no more lime than shall be sufficient for its complete precipitation, and I
then distil the liquor with additional lime and obtain the ammonia therefrom,
or after precipitating the zine I add an equivalent of sulphate of ammonia, and
having boiled it down to dryness sublime the muriate of ammonia. .2. I
precipitate the zinc with carbonate of soda or sulphide of sodium, the precipi-
tated carbonate or sulphide of zinc is then submitted to pressure and the
liquor extracted; to this liquor is then added the proper equivalent of sulphate

page_text: of ammonia, and the resulting sulphate of soda is extracted by boiling until its
crystals are precipitated, or the whole is boiled down to dryness and the muriate
of ammonia sublimed, whilst the sulphate of soda remains in the subliming
pot. 3. I precipitate the zinc with sulphide of barium, and after expressing
the liquor an equivalent of sulphate of ammonia is added, whereby the sulphate
of baryta is precipitated, and the liquor being expressed by pressure from this
precipitate will contain only the muriate of ammonia, which may be crystallised
or otherwise treated. 4. I add the proper equivalent of sulphate of ammonia,
and after boiling down to dryness sublime the muriate of ammonia and collect
the sulphate of zinc from the subliming pot. 5. I precipitate the oxide of
zinc with ammonia, and after expressing the liquor from the precipitate,
muriate of ammonia remains in the solution, which may be crystallised or other-
wise treated. 6. I treat the whole of the skimmings with sulphuric acid or
the soluble salts extracted from them, in precisely the same manner as salt is
treated in the manufacture of sulphate of soda, the muriatic acid being
condensed, and the resulting sulphates of zinc and ammonia left in the
decomposing pan may be separated by sublimation after crystallizing or boiling
down to dryness.
The second part of my Invention consists in refining the hard spelter,
commonly known as dross spelter, collected from the bottom of the baths of
zinc, and produced in the process of galvanizing or coating iron with zinc, and
I proceed as follows:-I charge the hard spelter into the retorts of an ordinary
Belgian furnace, but I only fill the retort about one half from the back end,
and I fill up the front part of the retort with ground coke or some inert
material, and place the ordinary condensing pipe on a descent or incline so
that the condensed zine shall not remain in it, but run out directly into a
proper receiver, whence it may be collected and afterwards melted and cast
into ingots; by adopting this mode of smelting or refining the hard metal I
am enabled to obtain a very pure metal and with very little loss from oxidation.
2. In lieu of the ordinary Belgian retort, which is cylindrical, I make the
retort of an oval or other convenient form, and before charging it with
zinc, I fill it up about one-third with ground coke or some inert material, so
that the iron contained in the hard spelter, instead of being deposited on the
bottom of the retort, which it destroys, may remain on the said inert material
and be withdrawn therewith without injury to the retort.
The third part of my Invention consists in collecting and condensing the
vapour arising from the galvanizing bath, or the bath used or employed in
coating iron with zine. This I do by conducting the vapours given off from
the bath by means of a hood or cover and a flue or flues into a tower filled.

page_text: with coke, upon and through amongst which I cause water, in a finely divided
state, to fall shower-like so that it percolates through the mass of coke and
coming into contact with the vapours condenses them. Or instead of using
coke in the manner described, I connect the flue with any suitable condenser,
and thus condense and collect the vapours.