Improvements in the Electro-deposition of the Heavy Metals.
Year: 1887

page_text: Date of Application, 9th June, 1887
Complete 'Left, 5th Mar., 1888
Complete Accepted, 27th Apr., 1888
Improvements in the Electro-deposition of the Heavy Metals.
I, SILVANUS PHILLIPS THOMPSON, of 20 Arundel Gardens, North Kensington, in
the County of Middlesex, Doctor of Science, do hereby declare the nature of this
invention to be as follows:-
My improvements relate to the electro-deposition of the heavy metals such as
platinum, iridium, palladium, ruthenium, and the like, and of their alloys, and have
for their object the obtaining of the deposits in a bright metallic form, also of
cheapening the preparation of the solution for producing such deposits.
The metal or alloy is first brought to the state of chloride by known chemical
processes. The chloride after having been dried at a moderate temperature, preferably
that of steam, is dissolved in distilled water or other soft water of adequate purity.
To this solution is added a solution of a certain medium, also previously similarly
dissolved, the weight of the medium taken being from 10 to 40 or 50 times as great
as that of the metallic chloride. As a medium I employ phosphate of soda, or
phosphate of soda mixed with borate of soda or carbonate of soda, or with tungstate
of soda, or with any of these materials, or I use the corresponding salt of ammonia
mixed with the soda salt as aforesaid.
The mixed solutions of metallic salt and medium are then heated together, preferably
to the boiling point; and to the liquor so produced I then add one of the following
brightening substances, namely, salammoniac, bromide of soda, carbonate of soda,
bicarbonate of soda, carbonate of ammonia, byposulphite of soda, hypochlorite of soda,
chlorate of soda, or a mixture of two or more of them, for example a mixture of
salammoniac and carbonate of soda. Preferably such brightening substances are also
similarly dissolved in a little water previously to being added to the solution. The
mixture having then been preferably once more heated it must be neutralised. If it
is found alkaline a few drops of hydrochloric acid or a solution of chlorine in water
or other suitable substance are cautiously added. If it is found acid carbonate or
bicarbonate of soda is added.
The bath so prepared should be warmed to a temperature of from 60° to 90°
(Centigrade) and is used in the ordinary well known way with a fairly strong electric

page_text: current. The anode may be of carbon, or of platinum; but in every case it will be
found requisite in the daily use of the bath to add (preferably hot) further quantities
of strong neutral metallic solution as the metal is withdrawn by deposition from the
bath, and also, from day to day to add small quantities of borate of soda or other
medium, and also of carbonate of soda or of hydrochloric acid or chlorine water to
correct the acidity or alkalinity of the bath.
As a typical example of my improved process the following quantities may be taken
for the deposition of bright-metallic platinum, viz..:-
Chloride of platinum two ounces, borate of soda one pound, carbonate of soda one
pound, salammoniae two ounces, the solution being finally made up with water to
one gallon.
Owing to the costly nature of the separated chlorides of the single metals, such as
chloride of iridium and chloride of platinum I prefer to employ a mixed metallic
chloride containing platinum with a certain admixture of iridium, ruthenium or the
like just as it occurs in or is derived from the natural ore. Grains of the natural ore
are treated with hot aqua regia to obtain the chlorides in solution; these being
subsequently boiled down to expel nitric acid. Or the mixed solution may be prepared
wholly or in part by electrolysis, the grains being placed on a plate of carbon or other
suitable anode and subjected in a chloride bath to the action of a current which slowly
dissolves out the more soluble part of the ore. The residue may be afterwards further
digested in aqua regia.

page_text: COMPLETE SPECIFICATION.
Improvements in the Electro-deposition of the Heavy Metals.
I, SILVANUS PHILLIPS THOMPSON, of 20 Arundel Gardens, North Kensington, in
the County of Middlesex, Doctor of Science, do hereby declare the nature of this
invention, and in what manner the same is to be performed, to be particularly.
described and ascertained in and by the following statement :-
My improvements relate to the electro-deposition of the heavy metals such as
platinum, iridium, palladium, ruthenium, and the like, and of their alloys, and have
for their object the obtaining of tho deposits in a bright metallic form, also of
cheapening the preparation of the solution for producing such deposits.
The metal or alloy is first brought to the state of chloride by known chemical
processes. The chloride after having been dried at a moderate temperature, preferably
that of steam, is dissolved in distilled water or other soft water of adequate purity.
To this solution is added a solution of a certain medium, also previously similarly
dissolved, the weight of the medium taken being from 10 to 40 or 50 times as great
as that of the metallic chloride. As a medium I employ phosphate of soda, or
phosphate of soda mixed with borate of soda or carbonate of soda, or with tungstate
of soda, or with any of these materials, or I use the corresponding salt of ammonia
mixed with the soda salt as aforesaid.
The mixed solutions of metallic salt and medium are then heated together, preferably
to the boiling point; and to the liquor so produced I then add one of the following
brightening substances, namely, salammoniac, bromide of soda, carbonate of soda,
bicarbonate of soda, carbonate of ammonia, hyposulphite of soda, hypochlorite of
soda, chlorate of soda, or a mixture of two or more of them, for example a mixture
of salammoniac and carbonate of soda. Preferably such brightening substances are
also similarly dissolved in a little water previously to being added to the solution.
The mixture having then been preferably once more heated it must be neutralised. If
it is found alkaline a few drops of hydrochloric acid or a solution of chlorine in water
or other suitable substance are cautiously added. If it is found acid carbonate or
bicarbonate of soda is added.
The bath so prepared should be warmed to a temperature of from 60° to 90°
(Centigrade) and is used in the ordinary well known way with a fairly strong electric
current. The anode may be of carbon, or of platinum; but in every case it will be
found requisite in the daily use of the bath to add (preferably hot) further quantities
of strong neutral metallic solution as the metal is withdrawn by deposition from the
bath, and also, from day to day to add small quantities of borate of soda or other
medium, and also of carbonate of soda or of hydrochloric acid or chlorine water to
correct the acidity or alkalinity of the bath.
As a typical example of my improved process the following quantities may be taken
for the deposition of bright metallic platinum, viz. :-
Chloride of platinum two ounces, borate of soda one pound, carbonate of soda one

page_text: pound, salammoniac two ounces, the solution being finally made up with water to
one gallon.
Owing to the costly nature of the separated chlorides of the single metals, such as
chloride of iridium and chloride of platinum I prefer to employ a mixed metallic
chloride containing platinum with a certain admixture of iridium, ruthenium or the
like just as it occurs in or is derived from the natural ore. Grains of the natural ore
are treated with hot aqua regia to obtain the chlorides in solution; these being
subseqently boiled down to expel nitric acid. Or the mixed solution may be prepared
wholly or in part by electrolysis, the grains being placed on a plate of carbon or other
suitable anode and subjected in a chloride bath to the action of a current which slowly
dissolves out the more soluble part of the ore. The residue may be afterwards further
digested in aqua regia.
I am aware that phosphate of soda and phosphate of ammonia and also chloride of
sodium in conjunction with chloride of platinum have already been suggested for use
in baths for the electro-deposition of the heavy metals, and I therefore lay no claim
to the use of such substances in themselves, but only their use in combination with
the other substances and in the manner described.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what I
claim is:-
In the electro-deposition of the heavy metals the use of a bath consisting of a
solution of the chloride of the metal, to which is added one or more of the media
above described, and after heating same one or more of the brightening substances
above described is or are added, the whole being then again preferably heated and
finally neutralised, all substantially as specified.