An improvement in Electrolytes for Deposit of Metals.
Year: 1899

page_text: I, PASCAL MARINO, of 77, Rue des Foulons, Brussels, Belgium, Chemist, do
hereby declare the nature of this invention to be as follows: --
This invention relates to electrolytes suitable for depositing metals such as
zinc, lead, tin, copper, or nickel, either pure or as alloys on other metals such
as iron, cast-iron or steel.
For this purpose, two solutions are prepared, the one consisting of neutral
ammonium tartrate in which are dissolved salts of the metals to be deposited,
the other consisting of magnesium sulphate and sodium pyrophosphate pre-
cipitated and re-dissolved in excess of the pyrophosphate; these solutions mixed
with addition of ammonium carbonate form an electrolyte from which the metal
or alloy of the metals contained in the first solution is deposited in a firm uniform
layer on metallic cathodes.
31
1
1000°
ABEL & IMRAY,
Agents for the Applicant.
An improvement in Electrolytes for Deposit of Metals.
I, PASCAL MARINO, of 77, Rue des Foulons, Brussels, Belgium, Chemist, 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 follow-
ing statement:—
This invention has for its object a process for producing electrolytic deposits
of metals, either pure or alloyed, especially of zinc, lead, tin, copper, or nickel,
on iron, cast iron or steel, as well as on other metals, by means of a first solution
of neutral ammonium tartrate in which is dissolved the salt of the metal to be
electrolytically deposited, and of a second solution of magnesium sulphate and
sodium pyrophosphate, so prepared that the ammonia does not precipitate the
magnesia. Practically, for the first solution, the neutral ammoniuni tartrate,
is prepared by adding 100 grams of ammonia solution of specific gravity
220 Baumé to one litre of a solution containing 170 grams of tartaric acid and
in this are dissolved the salts, preferably sulphates, of lead, tin, zinc, copper,
silver or nickel, in the proportion of 100 to 120 grams per litre. For the second
solution, a litre of a solution of sodium pyrophosphate of specific gravity
7000 Baumé is mixed with 25 c.c. of a solution of magnesium sulphate containing
12.5 grams; the white precipitate which is at first formed is dissolved in the
excess of the sodium pyrophosphate. This liquid does not precipitate salts of
silver, but sodium pyrophosphate alone without magnesium causes a white pre-
cipitate from these salts.

page_text: The two solutions being obtained as described, since ammonia does not pre-
cipitate magnesium sulphate, are mixed without fear of any precipitation. There
is then added a small quantity of ammonium carbonate, in proportion of 3 to 5
per cent. of the metal to be deposited. For electrolysis of tin, for instance, I
first prepare the hydrate of tin protoxide by treating protochloride with potas-
sium or sodium carbonate, causing disengagement of carbon-dioxide and of
hydrated tin protoxide which precipitates; I then saturate while hot dilute sul-
phuric acid with the tin hydrate which rapidly dissolves.
Afterwards I prepare the neutral ammonium tartrate by saturating a solution
of tartaric acid with ammonia, and to this I add the tin sulphate solution pre-
pared as above. For the other liquid I mix a solution of sodium pyrophosphate
and a solution of magnesium sulphate and dissolve the precipitate which is
formed in excess of sodium pyrophosphate; this solution being effected, I pour
it into the other solution of neutral ammonium tartrate and tin sulphate, and I
add ammonium carbonate till the mixture is quite limpid.
This electrolyte can be used at once to obtain metallic tin by a weak current.
For depositing alloys, two methods may be employed, either by mixing special
electrolytes of the metals which are to be deposited in alloy, or by dissolving
together salts of the metals to be deposited in alloy in proportion to the quantity
of each of the metals to be alloyed.
In this electrolyte the metals intended to be alloyed may be used as soluble
anodes.
The advantages of this electrolyte are:-
1. No free acid is produced, as occurs in ordinary electrolytic decomposition
of zinc sulphates, and consequently, (A) pieces of iron, steel, cast iron and zinc
which are to be covered when immersed in the bath, do not become oxidised
so as to render the deposit not adherent and not durable. (B). The metal
deposited on tlie cathode is not attacked.
2. Zinc by immersion without any electrical apparatus, becomes well coated
in the tin electrolyte.
This coating is uniform, adheres and resists strong friction and even
burnishing.
3. Pieces of iron, cast iron, steel or zinc can be coated with copper, brass,
bronze, &c., directly and in a very satisfactory regular manner.
4. The deposits of zine, lead or tin are not crystalline nor spongy, but form a
perfectly metallic layer with lustre, and whatever be its thickness there is no
surface roughness, and if the pieces have been well cleared of oxide, there is no
scaling off. These advantages are due chiefly to the electrolyte composition,
the first solution of which has a decomposing action, and the second (magnesium
and pyrophosphate) has a conducting action which favours passage of the
current.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim :-
The electrolyte above described consisting of two solutions the one of neutral
ammonium tartrate in which are dissolved salts of the metals to be deposited
the other of magnesium sulphate and sodium pyrophosphate precipitated and
re-dissolved in excess of the pyrophosphate, these solutions being mixed with
addition of ammonium carbonate.
Dated this 24th day of October 1899