IMPROVEMENTS IN PLATING OR COMBINING GOLD. PLATINUM, AND OTHER METALS OR THEIR ALLOYS
Year: 1865

page_text: PROVISIONAL SPECIFICATION left by Edward John Northward at the
Office of the Commissioners of Patents, with his Petition, on the 3rd
November 1865:
I, EDWARD JOHN NORTHWOOD, of Felix Place, Islington, in the County
of Middlesex, Bullion Refiner, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN PLATING OR COMBINING GOLD. PLATINUM, AND
OTHER METALS OR THEIR ALLOYS," to be as follows:-
My improvements consist, 1st, in the use of a malleable alloy or solder for
the fixing of one metal or alloy upon another by the medium of a third in a
process of fusion, and thus to produce a combination possessing eminent
malleable and ductile properties.
2ndly, in the disposition of the various metals or their alloys among them-
selves mentioned below, insomuch as their relative position is concerned,
thus as one metal or alloy upon one side, a second and different in the middle,
and a third upon the remaining face, or it may be three or more different
metals or alloys combined into one piece.
3rdly, in the use of the following metals in any process, viz., gold, silver,
platinum, palladium, aud copper, which may be used either separately oralloyed
among themselves in any convenient proportion, and also the use of alloys of
the above metals with tin, zinc, nickel, or aluminium.

page_text: 4thly, treating poor alloys of gold by an acid process by extracting a portion
of the alloy, and applying a coating of gold more or less fine upon the surface,
which is susceptible of being worked with the body after being submitted to
pressure either by lamination or drawing; also to close, and thus to render
more tough, the skin of gold alloy upon the surface by the application of
chloride ofgold in solution in either of the pores resulting from the extraction
of the alloy before the application of the condensing force.
5thly, the formation of leaf from alloys produced by this process.
I take an ingot of the alley to be plated, which must possess a higher
melting point than the solder with which the plate is to be cemented, of the
following dimensions:-Five inches by four inches and three-quarters of an
inch in thickness or thereabouts, and cleanse it with sand or einery paper.
It is perfectly flat upon each face having been cast in a skillet mould, or filed
to render it so, if necessary. I then prepare two pieces of sheet metal of
the alloy I propose to lay on by melting the alloy in a crucible in the usual
manner, and rolling the ingot in a sheet about one-quarter of an inch in
thickness, and ten inches by four inches in the other directions, which is cut
into two pieces, each being five inches by four inches.
This alloy must also have a higher melting point than the solder, which I
prepare in the following manner --Equal weights of fine silver and copper
are melted together in a crucible, and two pieces of sheet are made from the
ingot exactly four inches by three inches, and about one thirty-second part
of an inch in thickness, a more or less fusible solder may be produced by
varying the proportion of copper. I then lay upon the upper face of the
'metal to be plated one of the sheets of solder previously cleansed with emery
paper, and again upon that a sheet of the plating alloy likewise cleaned,
having previously surrounded the cage of the sheet of copper with a sheet of
copper exactly the thickness of the solder, and with the middle cut out to
exactly admit it. This is to prevent the outflow of the soldier when in a
state of fusion in a subsequent stage. I then place a piece of cast iron about
three-eighths of an inch thick, and six inches by five inches, perfectly
flat upon the top, invert the wliole, and treat the other face in a like
manner. The copper is of the same outside dimensions as the plating alloy,
thus admitting of a inargin of about half an inch around the solder for its
retention. When thus properly adjusted two inch iron clamps, with a
binding screw in the middle of each, are made to close the whole apparatus
by screwing up the iron plates, while the space between the edges of the
metal and those of the iron plates is filled with a composition of loam and
cowhair packed as a further precaution against the escape of solder. 1
:

page_text: next prepare a fire, in which is set a clay muffle similar to those used by
assayers, and consisting of a rectangular clay vessel of such capacity as to
admit the plates of metal to be operated upon, and allowing a space of about
one inch around to intervene between that and the vessel so that the progress
of the work may be observed. After the muffle has become red hot the
plates are introduced and laid upon a piece of tile in order to allow the
heated air to freely circulate beneath. Upon the uppermost iron plate I
stand a small cast-iron crucible or pyrometer to discover the exact time
when the operation of fusing the solder is at its turning point. The pyrometer
is a cylindrical vessel with a hemispherical cavity capable of containing about
one ounce of solder alloy in a lump, but charged only to the extent of five penny-
weights, the alloy being at the same time covered with borax to preserve it from
oxidation. The door of the muffle being closed and the temperature raised
a vigilant watch is kept through a small hole in the door upon the pyrometer
which indicates by the fusion of the lump of alloy the progress made. Im-
mediately the pyrometer indicates the complete fusion the plates are with-
drawn very carefully, allowed to cool, and the soldered plates taken out.
These plates are theu forged under the hammer, and ultimately rolled in the
ordinary manner by passing through flatting mills.
Wire. For wire I take a perfectly straight round piece of polished wire of
the metal I propose to plate, about six inches in length and three-quarters of
an inch thick. I then prepare a piece of the silver and copper solder exactly
one-thirty-second part of an inch in thickness, which I fit close upon its
whole length with the exception of about half an inch at each extremity,
which are closed with a ring or band of copper of exactly the same thick-
ness to prevent the escape of solder. Over the solder sheet I draw a pipe
of the metal with which it is proposed to plate, the two ends resting
upou their respective ring bands. The pipe is made by soldering the
two edges of a piece of sheet together after having been bent into the
tubular form, either with its own metal, as with platinum and gold tubes,
or by drawing a hollow cylinder upon a mandril. The pipe is made to
precisely fit the surface of the solder in order to exclude the air, and the
extremities over the copper bands are brought into closer contact by
the aid of two iron bands which embrace them, and are closed with the
assistance of screws to draw them together. The whole is then placed in a
wrought-iron tube, which in its turn is placed in a clay tube in the fire for the
purpose of fusing, as in the case of sheet metal before described. I then
hammer the plated rod until the plate and body become consolidated, and
draw it through steel plates in the ordinary manner.

page_text: For alloys of gold I adopt another process when the proportion of gold is
small, thus: Imix in a crucible six ounces of gold, four ounces of copper,and
four ounces of silver, for example, and thoroughly amalgamate them at a high
temperature, after which I cast it in a skillet mould. I then reduce the
thickness of the ingot of alloy in a pair of laminating rolls for the purpose
of closing the pores of the metal and producing a uniform surface. The
original thickness of the ingot employed found best to answer is one-
eighth of an inch, but it must not be reduced too thin, or the next
process is likely to render it rotten. I then prepare a mixture of pure
nitric acid and distilled water in equal proportions, into which I put the
sheets of alloy and boil for the space of one-quarter of an hour. I then
take the alloy out of the bath, wash it with warm water, and thoroughly dry
it. If a very thick coating of alloy is required I then immerse these sheets
in a bath of gold held in solution by ether, which evaporating when the sheets
are withdrawn deposits in the porous surface a mass of pure gold, which by
several immersions entirely occupies the place of the alloy extracted by the
acid process, and leaves a homogeneous body, which, after being passed several
times through the rolls, is rendered into "sheet" susceptible of being worked
into any shape. For wire it is only necessary to substitute drawing for
lamination.