Title of Invention	"AN IMPROVED PROCESS FOR THE PREPARATION OF IRIDIUM (IV) BROMIDE FROM IRIDIUM (III) CHLORIDE USEFUL FOR IRIDIUM PLATING"
Abstract	The present invention relates to an improved process for the preparation of iridium (IV) bromide useful for iridium plating. The process steps comprises heating iridium in the presence of an oxidizing agent such as herein described to red hot, cooling the resultant to 30°C and dissolved in distilled water, allowing the said solution to stand for 10-30 hours, reacting the resultant solution with potassium hydroxide at boiling temperature till a blue precipitate is formed, filtering the precipitate and heating it at 50-90°C with l-10ml of bromine and 10-150 ml of hydrobromic acid for 2-8 hours at a pH of 0.5 to 2.5 to get iridium (IV) bromide electrolyte.

Title of Invention

"AN IMPROVED PROCESS FOR THE PREPARATION OF IRIDIUM (IV) BROMIDE FROM IRIDIUM (III) CHLORIDE USEFUL FOR IRIDIUM PLATING"

Abstract

The present invention relates to an improved process for the preparation of iridium (IV) bromide useful for iridium plating. The process steps comprises heating iridium in the presence of an oxidizing agent such as herein described to red hot, cooling the resultant to 30°C and dissolved in distilled water, allowing the said solution to stand for 10-30 hours, reacting the resultant solution with potassium hydroxide at boiling temperature till a blue precipitate is formed, filtering the precipitate and heating it at 50-90°C with l-10ml of bromine and 10-150 ml of hydrobromic acid for 2-8 hours at a pH of 0.5 to 2.5 to get iridium (IV) bromide electrolyte.

Full Text	The present Invention relates to a process for the preparation of iridium (IV) bromide useful for iridium plating. The electrodeposited iridium apart from its decorative application, finds use for the tips of pen nibs and occassionally for gramophone record styli and the bearings of clocks and watches. Iridium alloy with platinum is used for porcelain dental restorations. Pure iridium has so far found few industrial applications because of its high cost. Interest in the development of coatings both for corrosion protection and for electrical contacts has focused attention on the electrode position of this platinum group metal. Hitherto, it has been proposed to electrode posit iridium from: (i) Fused salt baths. (J.C.Withers and P.E.Ritt, Tech. Pro. Am. Electroplaters Soc., 44th Ann. Conv., 1957, p 124). Iridium plating was done from a cyanide based fused salt bath containing iridium at 600°C in the current density ranges of 1 to 2A. dm-2, (ii) Sulphamate baths (Gordon A. Conn, Plating. (12) (1965) 1258 Iridium was deposited at a concentration of 8. 3 gpl as iridium (III) chloride (Varlocoid Chemical Company, 116 Broad Street. New York, 10006) and 42 gpl of sulphamic acid with a current density of 0.1 A. dm-2. The current efficiency was 63% at 90°C. (iii) Bromide bath (r. J.Tyrell. Trans.Inst. of Metal finish., 43 (1965) 161. Iridium deposition from iridium bromide bath gives an efficiency of 45% on titanium and 65% on gold undercoated copper, brass, nickel etc,. With 0.15A. dm-2 a current density, (iv) Chloro iridic acid bath. (E.L. McNamara, J.Electrochem. Soc., Jan. 1962, page No. 61. Iridium coating was made from chloro-iridic acid bath containing about 10gpl of iridium in the current density range of 2-9.0 A.dm-2 These have the following disadvantages: (I) The fused salt bath involve modern cyanides, causing environmental pollution. Also heating the substrate material to high temperature leads to changes in its physical properties. (II) Deposition from a sulphamate bath has the following drawbacks: (a) Works only in one specific make of the bath. (b) Sulphamic acid as its metal salt is likely to decompose at the bath temperature similar to the nickel salt. (c) Requires auxiliary a.c electrode. (III) The starting material for the preparation of the bromide was ammonium chloroiridate which is a very costly material compared to iridium chloride. The preparation requires continuous refluxing for extended periods to produce iridium oxide. This iridium oxide prepared is highly colloidal and difficult to filter incurring heavy loss of the oxide. Further the plating solution prepared from this bromide solution, can yield good deposits only on gold electroplated substrates like copper, nickel, brass and titanium. (IV) The chloroiridic acid electrolyte needs very high metal concentration (10 gpl of iridium) the current density was high (about 2.2 A/dm-2) and the cathode current efficiency is very poor, (around 14%) The main object of the present invention is to provide an improved process for the preparation of iridium (IV) bromide which obviates the drawbacks detailed above. The object is being achieved by oxidizing the iridium salt in the very beginning which enables easy settling of iridium oxide for complete filtration and also in the formation of a tetravalent bromide complex without any adulteration by the lower valent complex and this enables plating directly on substrates without the need for a gold undercoat. Accordingly the present invention provides an improved process for the preparation of iridium (IV) bromide from iridium (III) chloride useful for iridium plating which comprises heating iridium in the presence of an oxidizing agent such as herein described to red hot, cooling the resultant to 30°C and dissolved in distilled water, allowing the said solution to stand for 10-30 hours, reacting the resultant solution with potassium hydroxide at boiling temperature till a blue precipitate is formed, filtering the precipitate and heating it at 50-90°C with 1-10ml of bromine and 10-150 ml of hydrobromic acid for 2-8 hours at a pH of 0.5 to 2.5 to get iridium (IV) bromide electrolyte. In an embodiment of the present invention, the iridium (IIII) chloride containing 46-47% Ir, is heated with potassium chloride in presence of an oxidizing agent such as chlorine or hypochlorite to red heat. The reaction mixture after cooling is dissolved in distilled water and allowed to stand for 10-30 hours, reacting the resulting solution with potassium hydroxide at boiling temperature until a blue precipitate is formed which is filtered and heated with bromine and hydro bromic acid for 3 to 6 hrs and the pH is adjusted to 0.5 to 1.5. According to another embodiment of the invention, the process consists of fusing 1gm of iridium (iii) chloride with 0.5 - 5.0 gm of potassium chloride and l-10ml of 3-8 gpl hypochlorite till red heat, dissolving the fusion mixture in water and adding 1.0 - 10% of potassium hydroxide drop wise till the formation of a blue precipitate of hydrated iridium oxide, which after filtration is \refluxed with l-5mll of liquid bromine and twelve times of hydrobromic acid for 3 - 6 hrs, and making upto a required volume which was used for plating directly on copper, brass, nickel, titanium etc., The following typical examples are given to illustrate the invention and should not be construed to limit the scope of this invention. Example I 5 gms of aqueous Iridium chloride IrCl3 containing 47% of iridium, was heated with 2.5 gms potassium chloride and sodium hypochlorite in a silica crucible till red hot. The mixture after cooling was dissolved in water and allowed to stand overnight. The red colour solution obtained was heated to boiling, to which dilute boiling potassium hydioxide was added dropwise till a blue precipitate is formed. The pre-cipitate was filtered, dried and then mixed with bromine and hydrobromic acid and heated al 80°C for 4hrs. The blue colour solution was adjusted to pH 1.00 (and made up to 100ml for stock solution). Example. ...... II 5 gms of iridium (III) chloride was heated with 4.0 gms of potassium chloride in a current of chlorine till red hot. The mixture after cooling was dissolved in water and heated to boiling. To this, hot potassium hydroxide was added and the precipitated iridium oxide was filtered and dried. This powder was then dissolved in hydrobromic acid and boiled for 1 hour and the resultant solution was diluted and made as a stock solution. Example III To improve the precipitation of iridium oxide the potassium hydroxide treated solution was reduced with hydra-zine hydrate and then oxidised to iridium oxide using hydrogen peroxide. The hydrated iridium oxide thus obtained was refluxed with bromine and hydrobromic acid for 4hrs and used for electrodeposition of iridium. Example IV 5 gms of iridium (III) chloride was heated with 4.0 gms of potassium chloride and 5 ml of 30% V/o hydrogen peroxide. The mixture after cooling was dissolved in water and heated to boiling. To this potassium hydroxide was added and the precipitated iridium oxide was filtered and dried. This powder was dissolved in hydrobromic acid and boiled for 1 hour and the resultant solution was diluted and made as a stock solution. Iridium oxide was prepared directly from iridium (III) chloride. A boiling solution of iridium (III) chloride and potassium hydroxide, when mixed together, hydrated iridium oxide was obtained. This oxide was dissolved in boiling hydrobromic acid and was used for electrodeposition of iridiurn. Adherent deposition of iridium was obtained with a plating rate of lu/hr (10 cm.) and 55% current efficiency. The main Advantages of the present invention are: I. Eaiy to prepare and does not strictly requires laborious refluxing and enables easy settling of the oxide or thorough filtration and thus avoids loss of the oxide during filtration. II. The total conversion to the tetravalent state in the very begining ensures the formation of a complex of the same valency state. This enables direct deposition of iridium on many substrates without the need for a gold under coat. III.Adherent white deposits upto Sum (10-4cm)can be obtained directly on titanium for funtional applications. IV. Adherent bright deposits can be directly plated on copper, nickel, gold and brass sub strates. V. the process utilises a relatively cheaper and economic method of preparing the electrolyte than the conventional method using ammonium (chloroiridate. VI}, the stability of the bath is very good and can be used for extended periods of service. We Claim: 1. An improved process for the preparation of iridium (IV) bromide from iridium (III) chloride useful for iridium plating which comprises heating iridium in the presence of an oxidizing agent such as herein described to red hot, cooling the resultant to 30°C and dissolved in distilled water, allowing the said solution to stand for 10-30 hours, reacting the resultant solution with potassium hydroxide at boiling temperature till a blue precipitate is formed, filtering the precipitate and heating it at 50-90°C with l-10ml of bromine and 10-150 ml of hydrobromic acid for 2-8 hours at a pH of 0.5 to 2.5 to get iridium (IV) bromide electrolyte. 2. An improved process as claimed in Claim 1 wherein iridium chloride (III) is containing at least 46-47% Iridium. 3. An improved process as claimed in Claims 1&2 wherein the solution is allowed to stand for 15-20 hours. 4. An improved process as claimed in Claims 1-3 wherein potassium hydroxide used is in amount 1-10% and added drop wise till the formation of a blue precipitate. 5. An improved process for the preparation of iridium (IV) bromide from iridium (III) chloride useful fro iridium plating substantially as herein described with reference to the examples.

Full Text

The present Invention relates to a process for the preparation of iridium (IV) bromide useful for iridium plating.
The electrodeposited iridium apart from its decorative application, finds use for the tips of pen nibs and occassionally for gramophone record styli and the bearings of clocks and watches. Iridium alloy with platinum is used for porcelain dental restorations. Pure iridium has so far found few industrial applications because of its high cost. Interest in the development of coatings both for corrosion protection and for electrical contacts has focused attention on the electrode position of this platinum group metal.
Hitherto, it has been proposed to electrode posit iridium from:
(i) Fused salt baths. (J.C.Withers and P.E.Ritt, Tech. Pro. Am. Electroplaters Soc., 44th Ann. Conv., 1957, p 124).
Iridium plating was done from a cyanide based fused salt bath containing iridium at 600°C in the current density ranges of 1 to 2A. dm-2, (ii) Sulphamate baths (Gordon A. Conn, Plating. (12) (1965) 1258
Iridium was deposited at a concentration of 8. 3 gpl as iridium (III) chloride (Varlocoid Chemical Company, 116 Broad Street. New York, 10006) and 42 gpl of sulphamic acid with a current density of 0.1 A. dm-2. The current efficiency was 63% at 90°C. (iii) Bromide bath (r. J.Tyrell. Trans.Inst. of Metal finish., 43 (1965) 161.
Iridium deposition from iridium bromide bath gives an efficiency of 45% on titanium and 65% on gold undercoated copper, brass, nickel etc,. With 0.15A. dm-2 a current density, (iv) Chloro iridic acid bath. (E.L. McNamara, J.Electrochem. Soc., Jan. 1962, page No. 61.
Iridium coating was made from chloro-iridic acid bath containing about 10gpl of iridium in the current density range of 2-9.0 A.dm-2 These have the following disadvantages:
(I) The fused salt bath involve modern cyanides, causing environmental pollution.
Also heating the substrate material to high temperature leads to changes in its
physical properties.
(II) Deposition from a sulphamate bath has the following drawbacks:

(a) Works only in one specific make of the bath.
(b) Sulphamic acid as its metal salt is likely to decompose at the bath temperature
similar to the nickel salt.
(c) Requires auxiliary a.c electrode.

(III) The starting material for the preparation of the bromide was ammonium
chloroiridate which is a very costly material compared to iridium chloride. The
preparation requires continuous refluxing for extended periods to produce iridium
oxide. This iridium oxide prepared is highly colloidal and difficult to filter
incurring heavy loss of the oxide. Further the plating solution prepared from this
bromide solution, can yield good deposits only on gold electroplated substrates
like copper, nickel, brass and titanium.
(IV) The chloroiridic acid electrolyte needs very high metal concentration (10
gpl of iridium) the current density was high (about 2.2 A/dm-2) and the cathode
current efficiency is very poor, (around 14%)
The main object of the present invention is to provide an improved process for the preparation of iridium (IV) bromide which obviates the drawbacks detailed above.
The object is being achieved by oxidizing the iridium salt in the very beginning which enables easy settling of iridium oxide for complete filtration and also in the formation of a tetravalent bromide complex without any adulteration by the lower valent complex and this enables plating directly on substrates without the need for a gold undercoat.
Accordingly the present invention provides an improved process for the preparation of iridium (IV) bromide from iridium (III) chloride useful for iridium plating which
comprises heating iridium in the presence of an oxidizing agent such as herein described to red hot, cooling the resultant to 30°C and dissolved in distilled water, allowing the said solution to stand for 10-30 hours, reacting the resultant solution with potassium hydroxide at boiling temperature till a blue precipitate is formed, filtering the precipitate and heating it at 50-90°C with 1-10ml of bromine and 10-150 ml of hydrobromic acid for 2-8 hours at a pH of 0.5 to 2.5 to get iridium (IV) bromide electrolyte.
In an embodiment of the present invention, the iridium (IIII) chloride containing 46-47% Ir, is heated with potassium chloride in presence of an oxidizing agent such as chlorine or hypochlorite to red heat. The reaction mixture after cooling is dissolved in distilled water and allowed to stand for 10-30 hours, reacting the resulting solution with potassium hydroxide at boiling temperature until a blue precipitate is formed which is filtered and heated with bromine and hydro bromic acid for 3 to 6 hrs and the pH is adjusted to 0.5 to 1.5.
According to another embodiment of the invention, the process consists of fusing 1gm of iridium (iii) chloride with 0.5 - 5.0 gm of potassium chloride and l-10ml of 3-8 gpl hypochlorite till red heat, dissolving the fusion mixture in water and adding 1.0 - 10% of potassium hydroxide drop wise till the formation of a blue precipitate of hydrated iridium oxide, which after filtration is \refluxed with l-5mll of liquid bromine and twelve times of hydrobromic acid for 3 - 6 hrs, and making upto a required volume which was used for plating directly on copper, brass, nickel, titanium etc.,
The following typical examples are given to illustrate the invention and should not be construed to limit the scope of this invention.
Example I
5 gms of aqueous Iridium chloride IrCl3 containing 47% of iridium, was heated with 2.5 gms potassium chloride and sodium hypochlorite in a silica crucible till red hot. The mixture after cooling was dissolved in water and allowed to stand overnight. The red colour solution obtained was heated
to boiling, to which dilute boiling potassium hydioxide was added dropwise till a blue precipitate is formed. The pre-cipitate was filtered, dried and then mixed with bromine and hydrobromic acid and heated al 80°C for 4hrs. The blue colour solution was adjusted to pH 1.00 (and made up to 100ml for stock solution).
Example. ...... II
5 gms of iridium (III) chloride was heated with 4.0 gms of potassium chloride in a current of chlorine till red hot. The mixture after cooling was dissolved in water and heated to boiling. To this, hot potassium hydroxide was added and the precipitated iridium oxide was filtered and dried. This powder was then dissolved in hydrobromic acid and boiled for 1 hour and the resultant solution was diluted and made as a stock solution.
Example III
To improve the precipitation of iridium oxide the potassium hydroxide treated solution was reduced with hydra-zine hydrate and then oxidised to iridium oxide using hydrogen peroxide. The hydrated iridium oxide thus obtained was refluxed with bromine and hydrobromic acid for 4hrs and used for electrodeposition of iridium.
Example IV
5 gms of iridium (III) chloride was heated with 4.0 gms of potassium chloride and 5 ml of 30% V/o hydrogen peroxide. The mixture after cooling was dissolved in water and heated to boiling. To this potassium hydroxide was added and the precipitated iridium oxide was filtered and dried. This powder was dissolved in hydrobromic acid and boiled for 1 hour and the resultant solution was diluted and made as a stock solution.
Iridium oxide was prepared directly from iridium (III) chloride. A boiling solution of iridium (III) chloride and potassium hydroxide, when mixed together, hydrated iridium oxide was obtained. This oxide was dissolved in boiling hydrobromic acid and was used for electrodeposition of
iridiurn. Adherent deposition of iridium was obtained with a plating rate of lu/hr (10 cm.) and 55% current efficiency.
The main Advantages of the present invention are:
I. Eaiy to prepare and does not strictly requires
laborious refluxing and enables easy settling
of the oxide or thorough filtration and thus
avoids loss of the oxide during filtration.
II. The total conversion to the tetravalent state
in the very begining ensures the formation of
a complex of the same valency state. This
enables direct deposition of iridium on many
substrates without the need for a gold under
coat.
III.Adherent white deposits upto Sum (10-4cm)can be obtained directly on titanium for funtional applications.
IV. Adherent bright deposits can be directly plated on copper, nickel, gold and brass sub strates.
V. the process utilises a relatively cheaper and economic method of preparing the electrolyte than the conventional method using ammonium (chloroiridate.
VI}, the stability of the bath is very good and can be used for extended periods of service.

We Claim:
1. An improved process for the preparation of iridium (IV) bromide from iridium
(III) chloride useful for iridium plating which comprises heating iridium in the
presence of an oxidizing agent such as herein described to red hot, cooling the
resultant to 30°C and dissolved in distilled water, allowing the said solution to
stand for 10-30 hours, reacting the resultant solution with potassium hydroxide at
boiling temperature till a blue precipitate is formed, filtering the precipitate and
heating it at 50-90°C with l-10ml of bromine and 10-150 ml of hydrobromic acid
for 2-8 hours at a pH of 0.5 to 2.5 to get iridium (IV) bromide electrolyte.
2. An improved process as claimed in Claim 1 wherein iridium chloride (III) is
containing at least 46-47% Iridium.
3. An improved process as claimed in Claims 1&2 wherein the solution is allowed to
stand for 15-20 hours.
4. An improved process as claimed in Claims 1-3 wherein potassium hydroxide used
is in amount 1-10% and added drop wise till the formation of a blue precipitate.
5. An improved process for the preparation of iridium (IV) bromide from iridium
(III) chloride useful fro iridium plating substantially as herein described with
reference to the examples.

Documents:

400-del-2001-abstract.pdf

400-del-2001-claims.pdf

400-del-2001-correspondence-others.pdf

400-del-2001-correspondence-po.pdf

400-del-2001-description (complete).pdf

400-del-2001-form-1.pdf

400-del-2001-form-18.pdf

400-del-2001-form-2.pdf

400-del-2001-form-3.pdf

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Patent Number

230756

Indian Patent Application Number

400/DEL/2001

PG Journal Number

11/2009

Publication Date

13-Mar-2009

Grant Date

27-Feb-2009

Date of Filing

29-Mar-2001

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110 001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	SUBRAMANIAN PUSHPAVANAM	CECRI KARAIKUDI
2	GOKULAN SHEELA	CECRI KARAIKUDI
3	MALATHY PUSHPAVANAM	CECRI KARAIKUDI

PCT International Classification Number

C01G 55/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA