IMPROVEMENTS IN THE PREPARATION AND PRESERVATION OF AN ELECTRO-DEPOSITING SOLUTION OF NICKEL
Year: 1877

page_text: LETTERS PATENT to John Unwin, of Sheffield, in the County of York, Manu-
facturer and Merchant, for the Invention of "IMPROVEMENTS IN THE
PREPARATION AND PRESERVATION OF AN ELECTRO-DEPOSITING SOLUTION OF
NICKEL"
Sealed the 13th October 1877, and dated the 20th April 1877.
PROVISIONAL SPECIFICATION left by the said John Unwin at the Office
of the Commissioners of Patents on the 20th April 1877.
JOHN UNWIN, of Sheffield, in the County of York, Manufacturer and Merchant.
" IMPROVEMENTS IN THE PREPARATION AND PRESERVATION OF AN ELECTRO-
DEPOSITING SOLUTION OF NICKEL"
My Invention relates, firstly, to the preparation of a solution of nickel intended
for use in the electro-deposition of nickel in a pure or slightly alloyed state upon
iron, copper, and other metallic and conducting surfaces; and, secondly, to the preser-
vation or keeping of such solution in good working order, and restoring it to good
condition when out of order through its contamination with foreign matters derived
from the anode, &c.
To effect the first object of my Invention I prepare a pure double sulphate of
nickel and ammonia, in the following manner :-I first prepare a solution of sulphate
of nickel, by taking three parts of strong nitric acid (Sp. Gr.=about 1.400), one
part of strong sulphuric acid (Sp. Gr. about 1-840), and four parts of water, all by
measure, mixing them, cautiously, and about half filling an open earthenware pan
with the mixture. To every gallon of this mixed acid I then add about two pounds
of ordinary grain or cube nickel, and I heat the liquid by a sand bath or other
suitable means. If during the process of solution the action become inconveniently
violent, I moderate it by the addition of a little cold water. If the nickel entirely
dissolves (except a small quantity of light black matter), I add more of it in small
portions at a time, and continue the addition at intervals until it is in excess; when
the production of red fumes has nearly or entirely ceased, or when the liquid becomes
thick and pasty from the separation of solid sulphate of nickel, I add a moderate
quantity of hot water, boil and filter the solution; the deep green liquid so obtained.

page_text: is a strong solution of sulphate of nickel. If from the circumstances of its production
I consider that it requires purification, I concentrate the solution by evaporation,
until on cooling it yields a considerable per-centage of crystals of sulphate of nickel ;
these crystals I collect, wash with a little cold water, and re-dissolve in a moderate
quantity of hot water, filtering again if necessary. When cold, the liquid is ready
for further treatment. I do not make any claim to originality in the above des-
cribed method of preparing the sulphate of nickel by itself, as it is nearly identical
with that described by me in the Specification of Letters Patent granted to me and
bearing date Decr. 21, 1871, No. 3459, but I do claim the method of obtaining a
pure double sulphate of nickel and ammonia, to be presently described, and in which
the sulphate of nickel prepared as above is employed.
I next prepare a strong solution of sulphate of ammonia by dissolving the salt in
hot water, in proportion of about four pounds of the salt to each gallon of water,
and then filter the liquid if necessary and allow it to become cold. I then obtain
the pure double sulphate of nickel and ammonia by adding the above described
solution of sulphate of ammonia to that of the sulphate of nickel obtained as herein-
above described; but I do not stop the addition of the solution of sulphate of
ammonia when sufficient has been added to combine with all the sulphate of
I do this because I
nickel present, but I continue to add it in large excess.
have discovered that the double sulphate of nickel and ammonia is far less
soluble in the solution of sulphate of ammonia than in pure water, so that it
is precipitated from its solution in water on adding sulphate of ammonia. I there-
fore continue adding the solution of sulphate of ammonia, continuously stirring until
the liquid loses nearly all its colour, by which time the double sulphate of nickel-
and ammonia will have been precipitated as a light blue crystalline powder which
readily settles to the bottom of the vessel. I then pour off the liquid from the
crystalline precipitate of double sulphate of nickel and ammonia, and wash the
Jatter quickly with a strong cold solution of sulphate of ammonia as often as I.
consider necessary for its sufficient purification, but I do not throw away this liquid
after use, but employ it at my discretion for combining with fresh sulphate of nickel
instead of dissolving a further amount of sulphate of ammonia.
If I desire to make a further purification of the double sulphate of nickel and ammonia
I make a strong solution of it in distilled water, and add to the liquid a strong solu-
tion of sulphate of ammonia, by which means the double sulphate is precipitated in
a very pure condition and is separated from the liquid by filtration or other con-
venient means, and then dried or used direct, as may be desired; the liquid strained
away can be employed instead of fresh solution of sulphate of ammonia for
combining with more sulphate of nickel, or for washing the precipitate of double
sulphate.
The above described method of preparing a pure double sulphate of nickel and
ammonia differs essentially from that described by William Brookes in the
Specification of Letters Patent granted to him, and bearing date Oct. 28, 1869,
No. 3125, inasmuch as I omit the long and tedious evaporations and circuitous mode
employed by him to purify his sulphate of nickel, as have discovered that they
are wholly unnecessary; I further wash, re-dissolve, and re-precipitate my double
sulphate of nickel and ammonia, which processes are wholly omitted in the said
referred to Invention.
The said above described method differs also from that described by me in the
Specification of my said former Patent in the facts that I then mixed the solutions
of sulphate of nickel and of sulphate of ammonia when hot, and I now mix them
when cold; and I then directed the addition of "sulphate of ammonia to the boiling
solution of sulphate of nickel until I had neutralized all the acid in the solution,"
and then obtained and purified the solid double sulphate by cooling and crystalliza-
tion;
but I now obtain it from its solution by precipitating it with a large excess of
sulphate of ammonia, having discovered its very sparing solubility in a solution of
the latter salt, which fact I also utilize for its washing and purification. I then
prepare the depositing solution (subsequently to be used for the purpose of depositing

page_text: the nickel) by taking the before referred to crystals or crystalline precipitate of the
double sulphate of nickel and ammonia, and dissolving them in hot distilled water
and allowing the whole to cool; I then add cold distilled water until the solution is
of about the specific gravity of 6° by Twaddle's hydrometer, equal to an absolute
specific gravity of about 1030 (water=1000). I then test the solution with litmus
paper. If the liquid is perfectly neutral, I add a very small quantity of sulphuric
acid, so that blue litmus paper may be reddened; or I add a small quantity of
solution of ammonia, so that red litmus paper may be turned blue.
Having thus obtained a slightly acid or alkaline solution, the liquid is ready for
use in the electro-deposition of the metal on the surfaces required in the usual
manner. I do not claim the sole use of acid or alkaline solutions of the double
sulphate of nickel and ammonia for the electro-deposition of nickel (for which pur-
pose they have previously been employed) except when the double sulphate has
been prepared as herein-above described.
To effect the second object of my Invention I employ ammonia alum, which I use
in the following manner :-I take about an ounce of alum for every gallon of the
solution to be purified, and dissolve it in a small quantity of hot water, and add the
solution so obtained to the nickel solution, stirring well to obtain a perfect admixture.
If the liquid does not then turn red litmus paper blue I add sufficient solution of
ammonia to cause that effect, and then allow the flocculent precipitate thus pro-
duced to settle. I then draw or strain off the clear liquid from the deposit and use
the former for electro-depositing in the ordinary way. I also employ for this purpose
potash alum or sulphate of alumonia or other suitable compound of aluminima, but
I prefer the use of ammonia-alum.
"
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John Unwin in the Great Seal Patent Office on the 19th
October 1877.
JOHN UNWIN, of Sheffield, in the County of York, Manufacturer and Merchant.
IMPROVEMENTS IN THE PREPARATION AND PRESERVATION OF AN ELECTRO-
DEPOSITING SOLUTION OF NICKEL."
My Invention relates, firstly, to the preparation of a solution of nickel intended
for use in the electro-deposition of nickel in a pure or slightly alloyed state upon
iron, copper, and other metallic and conducting surfaces; and secondly, to the pre-
servation or keeping of such solution in good working order and restoring it to good
condition when out of order through its contamination with foreign matters derived
from the anode, &c.
To effect the first object of my Invention I prepare a pure double sulphate of
nickel and ammonia in the following manner:-I first prepare a solution of sulphate
of nickel by taking three parts of strong nitric acid (Sp. Gr.=about 1·400) one part
of strong sulphuric acid (Sp. Gr. about 1-840), and four parts of water, all by
measure, mixing them cautiously and about half filling an open earthenware pan
with the mixture. To every gallon of this mixed acid I then add about two pounds
of ordinary grain or cube nickel, and I heat the liquid by a sand bath or other
suitable means. If during the process of solution the action become inconveniently
violent, I moderate it by the addition of a little cold water. If the nickel entirely
dissolves (except a small quantity of light black matter), I add more of it in small
portions at a time, and continue the addition at intervals until it is in excess. When
the production of red fumes has nearly or entirely ceased, or when the liquid becomes
thick and pasty from the separation of solid sulphate of nickel, I add a moderate
quantity of hot water, and boil and filter the solution; the deep green liquid so
obtained is a strong solution of sulphate of nickel. If from the circumstances of its
production I consider that it requires purification, I concentrate the solution by

page_text: evaporation until on cooling it yields a considerable per-centage of crystals of sulphate
of nickel; these crystals I collect, wash with a little cold water, and re-dissolve in a
moderate quantity of hot water, filtering again if necessary. When cold the liquid
is ready for further treatment. I do not make any claim to originality in the above-
described method of preparing the sulphate of nickel by itself, as it is nearly identical
with that described by me in the Specification of Letters Patent granted to me, and
bearing date December 21, 1871, No. 3459, but I do claim the method of obtaining a
pure double sulphate of nickel and ammonia, to be presently described, and in which
the sulphate of nickel prepared as above is employed.
I next prepare a strong solution of sulphate of ammonia by dissolving the salt in
hot water, in the proportion of about four pounds of the salt to each gallon of water,
and then filter the liquid if necessary, and allow it to become cold. I then obtain
the pure double sulphate of nickel and ammonia by adding the above described
solution of sulphate of ammonia to that of the sulphate of nickel, obtained as
herein-above described, but I do not stop the addition of the solution of sulphato of
ammonia when sufficient has been added to combine with all the sulphate of nickel
present, but I continue to add it in large excess. I do this because I have discovered
that the double sulphate of nickel and ammonia is far less soluble in the solution of
sulphate of ammonia than in pure water, so that it is precipitated from its solution
in water on adding sulphate of ammonia. I therefore continue adding the solution
of sulphate of ammonia, continuously stirring until the liquid loses nearly all its
colour, by which time the double sulphate of nickel and ammonia will have been
precipitated as a light blue crystalline powder which readily settles to the bottom of
the vessel. I then pour off the liquid from the crystalline precipitate of double
sulphate of nickel and ammonia, and wash the latter quickly with a strong cold
solution of sulphate of ammonia, as often as I consider necessary for its sufficient
purification, but I do not throw away this liquid after use, but employ it at my
discretion for combining with fresh sulphate of nickel instead of dissolving a further
amount of sulphate of aminonia.
If I desire to make a further purification of the double sulphate of nickel and
ammonia I make a strong solution of it in distilled water, and add to the liquid
a strong solution of sulphate of ammonia, by which means the double sulphate is
precipitated in a very pure condition, and is separated from the liquid by filtra-
tion or by other convenient means, and then dried, or used direct as may be desired;
the liquid strained away can be employed instead of fresh solution of sulphate of
ammonia for combining with more sulphate of nickel, or for washing the precipitate
of the double sulphate.
The above described method of preparing a pure double sulphate of nickel and
ammonia differs essentially from that described by William Brookes in the Specifi-
cation of Letters Patent granted to him, and bearing date October 28, 1869, No.
3125, inasmuch as I omit the long and tedious evaporations and circuitous mode
employed by him to purify his sulphate of nickel, as I have discovered wholly un-
necessary; I further wash or re-dissolve and re-precipitate my double sulphate of
nickel and ammonia, which processes are wholly omitted or rather not comprised in
the said referred to Invention.
The said above-described method differs also from that described by me in the
Specification of my said former Patent in the facts that I then mixed the solutions
of sulphate of nickel and of sulphate of ammonia when hot, and I now mix them when
cold and I then directed the addition of "sulphate of ammonia to the boiling
solution of sulphate of nickel until I had neutralized all the acid in the solution,"
and then obtained and purified the solid double sulphate by cooling and crystalliza-
tion; but I now obtain it from its solution by precipitating it with a large excess
of sulphate of ammonia, having discovered its very sparing solubility in a solution
of the latter salt, which fact I also utilize for its washing and purification. I then
prepare the depositing solution (subsequently to be used for the purpose of depositing
the nickel) by taking the before referred to crystals or crystalline precipitate of the
double sulphate of nickel and ammonia, and dissolving them in hot distilled water,

page_text: and allowing the whole to cool; I then add cold distilled water until the solution is
of about the specific gravity of 7° by Twaddle's hydrometer, equal to an absolute specific
gravity of about 1030 (water=1000). I then test the solution with litmus paper.
If the liquid is perfectly neutral, I add a very small quantity of sulphuric acid, s0
that blue litmus paper may be reddened, or I add a small quantity of solution of
ammonia, so that red litmus paper may be turned blue.
Having thus obtained a slightly acid or alkaline solution, the liquid is ready for
use in the electro-deposition of the metal on the surfaces required in the usual
manner. I do not claim the sole use of acid or alkaline solutions of the double sul-
phate of nickel and ammonia for the electro-deposition of nickel (for which purpose
they have previously been employed) except when the said double sulphate has boen
prepared as herein-above described.
To effect the second object of my Invention I employ ammonia alum, which I use
in the following manner:-I take about an ounce of alum for every gallon of the
solution to be purified, and dissolve it in a small quantity of hot water, and add the
solution so obtained to the nickel solution, stirring well to obtain a perfect admixture.
If the liquid does not then turn red litmus paper blue I add sufficient solution of
ammonia to cause that effect, and then allow the flocculent precipitate thus produced
to settle. I then draw or strain off the clear liquid from the deposit and use the
former for electro-depositing in the ordinary way. I also employ for this purpose
potash alum or sulphate of alumonia, or other suitable compound of aluminima, but
I prefer the use of ammonia alum.
Having now described the nature and object of my said Invention, together
with the manner in which the same is to be or may be performed or carried
into practical effect, I would remark in conclusion that I claim as my Invention,―
First. The preparation of a slightly acid or alkaline electro-depositing solution
of nickel, by firstly preparing a pure double sulphate of nickel and ammonia, sub-
stantially as herein-above described, and subsequently treating such double sulphate
also, substantially as herein-above described.
Second. The use of the solution of nickel prepared by this improved method in
the electro-deposition of nickel upon any required and conducting surfaces.
Third. The purifying and restoring to good condition of the said solution of nickel,
when out of order, and the preserving or keeping of it in good working condition
by the treatment thereof with a solution of aminonia alum, potash alum, or sulphate
of ammonia, or other suitable compound of aluminima, substantially as herein-above
described.
And, Fourth. The preparation of the said pure double sulphate of nickel and
ammonia by the mixing of a solution of sulphate of nickel prepared as herein-above
described, with a solution of sulphate of ammonia, also prepared as herein-above
described, with the addition of a large excess of the latter salt, so as to cause a
precipitation of the double sulphate from its state of solution, and the subsequent
purification of the precipitated double sulphate by washing with a solution of sulphate
of ammonia, and by solution in water and reprecipitation from such solution by the
addition of sulphate of ammonia, substantially as herein-above described.
In witness whereof, I, the said John Unwin, have hereunto set my hand and
seal, this Tenth day of October, in the year of our Lord One thousand eight
hundred and seventy-seven,
JOHN UNWIN. (L.S.)