EXAMPLE 1

Preparation of Various Dithionate Salts and/or Dithionic Acid

[0064] 1(a) Preparation of Manganese Dithionate

[0065] A jacketed 1 liter reactor was equipped with a mechanical stirrer, an addition funnel, a thermocouple thermometer and a gas inlet and outlet. The reactor was charged with 500 ml of DI water. The moderately stirred water was cooled by circulating a glycol cooling fluid through the external jacket until the water temperature was reduced to 10° C. The cooled water was saturated with gaseous SO ₂ (1 g/min, 300 g total). Next, a slurry of manganese dioxide was created by mixing together 89 g MnO ₂ (92% pure battery grade) and 50 g of DI water, and this slurry was slowly added (addition funnel) over about 1 hour to the aqueous SO ₂ . A continuous flow of SO ₂ (g) was maintained during the MnO ₂ addition, and the temperature was maintained between 10° C. to 15° C. After the MnO ₂ addition (solution usually becomes clear pink within 10 minutes), the SO ₂ (g) flow and the cooling was stopped. The excess SO ₂ was removed by passing N ₂ (g) through the gently heated (app. 40° C.) solution over about 10 hours. Finally, a clear pink solution was obtained (82% yield of manganese dithionate by IC analysis based on MnO ₂ , 2%-3% sulfate impurity also by IC analysis).

[0066] 1(b) Preparation of the Barium Dithionate.

[0067] To a vigorously stirred manganese dithionate solution (all of the solution from 1 a) at room temperature was added over 20 minutes Ba(OH) ₂ .8H ₂ O (290 grains) dissolved in 400 ml of DI water at 80° C. Vigorous stirring was maintained for about 3 hours. The white suspension was then filtered (note that the white manganese oxide collected in the filter turns brown and gummy when left in the air) to isolate pure aqueous barium dithionate (79% yield by IC analysis based on MnO ₂ ).

[0068] 1(c) Preparation of Copper Dithionate

[0069] A 2 liter flask was charged with an aqueous solution of barium dithionate (all of the solution from 1 b) and an equimolar amount of solid CuSO ₄ (a very concentrated aqueous solution can be used, addition with vigorous stirring). Vigorous stirring was maintained for about 3 hours following which time the white suspension of BaSO ₄ was filtered. The resulting deep blue solution of copper dithionate was evaporated in-vacuo to yield solid copper dithionate as a blue crystalline material (approximately 55% yield based on MnO ₂ with less than 0.8% sulfate impurity by IC analysis).

[0070] 1(d) Preparation of Stannous Dithionate

[0071] Manganese dithionate and then barium dithionate as prepared as in Example 1(a) and 1(b).

[0072] A 2 liter flask equipped with a gas inlet/outlet was charged with an aqueous solution of barium dithionate, and a slow flow of nitrogen was initiated in order to purge the reactor of oxygen. An equimolar amount of solid SnSO ₄ was added to the barium dithionate with vigorous stirring. The vigorous stirring and the nitrogen purge were maintained for about 3 hours following which time the white suspension of BaSO ₄ was filtered. The clear solution of stannous dithionate obtained was usually used as is (evaporation in-vacuo led to excessive oxidation of Sn ⁺² to Sn ⁺⁴ ) (approximately 57% yield based on the amount of MnO ₂ originally used with less than 0.6% sulfate impurity by IC analysis).

[0073] 1(e) Preparation of Mixed Dithionic Acid & Stannous Dithionate

[0074] A 2 liter flask equipped with a gas inlet and outlet was charged with an aqueous solution of barium dithionate (prepared as in Example 1b), and a slow flow of nitrogen was initiated. A 2 molar amount of solid SnSO ₄ was added with vigorous stirring. The vigorous stirring and the nitrogen flow were maintained for about 1 hour, and then a ½ molar amount of sulfuric acid was added. The vigorous stirring and the nitrogen flow were maintained for another 2 hours after which tine the white suspension of BaSO ₄ was filtered. The clear filtrate of mixed dithionic acid and stannous dithionate was then used as is (approximately 70% yield with less than 1% sulfate impurity by IC analysis).

[0075] 1(f) Preparation of Mixed Dithionic Acid & Cupric Dithionate

[0076] A 2 liter flask was charged with an aqueous solution of barium dithionate (prepared as in Example 1b) and a 2 molar amount of solid CuSO ₄ with vigorous stirring. Stirring was continued for about 1 hour and then a 2 molar amount of sulfuric acid was added with continued vigorous stirring. Stirring was again maintained for about 2 hours following which time the white suspension of BaSO ₄ was filtered. The clear blue solution of mixed dithionic acid and cupric dithionate was then used as is (approximately 50% yield based on the MnO ₂ originally used with less than 1.5% sulfate impurity by IC analysis).

[0077] 1(g) Preparation of Ammonium Dithionate

[0078] An aqueous solution of manganese dithionate (formed as in Example 1a) was treated with a 50% mole excess quantity of (NH ₄ ) ₂ CO ₃ added as an aqueous solution over about 20 minutes with vigorous stirring (take care to control CO ₂ gas evolution during this step). Vigorous stirring was maintained for about 3 hours and then the white suspension was filtered (note that the solid manganese carbonate isolated in the filter slowly turns brown and gummy upon exposure to air). The clear ammonium dithionate solution isolated was evaporated in-vacuo to yield solid ammonium dithionate as a white crystalline material (95% yield based on the MnO ₂ originally used with less than 1.6% sulfate impurity by IC analysis).

[0079] 1(h) An Identical Procedure Can be Used for the Preparation of bis(2-ammonium-2-methyl-1-propanol)dithionate. Bis(2-ammonium-2-methyl-1-propanol Carbonate was Obtained by Saturating a Solution of 2-amino-2-methyl-1-propanol (AMP) with CO ₂ Followed by the Addition of a Second Equivalent of AMP).

[0080] 1(i) Preparation of Mixed Sodium/Magnesium Dithionate by Ion-Exchange

[0081] A jacketed glass reactor equipped with a source of SO ₂ and a N ₂ (g) sparge was charged with 1 Kg of DI water. The water was cooled to 10° C. and then saturated with gaseous sulfur dioxide (required app. 200 g of SO ₂ ). To the aqueous SO ₂ solution, 160 grams of battery grade manganese dioxide (0.54 moles) was added over several hours such that the temperature remained between 10° C. and 15° C. The finely powdered MnO ₂ reacted rapidly with a slight exotherm. Upon completion of the MnO ₂ addition, the excess SO ₂ was removed by heating the solution to 40° C. under a N ₂ (g) sparge for 8 hours. Next, an aqueous solution of sodium carbonate (57.6 grams, 0.54 moles) was added to the well stirred solution of manganese dithionate over 30 minutes. The precipitated manganese carbonate was removed by vacuum filtration through a 1 micron glass microfibre pad, and the aqueous sodium dithionate filtrate was collected. The filtrate was reduced in-vacuo to a solid. The product was isolated as the solid dihydrate in greater than 95% yield based on MnO ₂ . Next, a portion of the isolated sodium dithionate (23.4 grams, 97 mmol) was dissolved in 100 g of DI water, and to this approximately 1 M aqueous solution of sodium dithionate was added 50 grams of the proton form of Amberlyst 36W cation-exchange resin (app. 260 mmol of protons). The heterogenous mixture was stirred at RT for 10 minutes. The acidified aqueous dithionate solution was filtered free of the ion-exchange resin and then added to a beaker containing solid magnesium hydroxide (100 mmol). The suspension was stirred and gently heated for 1 hour. The solution was filtered free of solid material and then evaporated in-vacuo to yield 25 grains of a solid which by IC and ICP/emission analysis was 70.5% S ₂ O ₆ ⁻² , 0.7% SO ₄ ⁻² , 4.8% Mg ⁺² and 6.6% Na ⁺ .

EXAMPLE 2

Acid Tin Electroplating

[0082] Several formulations were tested, and results were compared through the analysis of electrodeposit quality (surface XRF and visual inspection). The formulations were prepared and used at room temperature. The electroplating experiments were performed in a 267 ml Hull Cell with bright brass plated steel panels and moderate mechanical agitation. The panels were pretreated by exposure to 40 ASF of cathodic current for two minutes in an alkaline phosphate solution at 60° C. followed by a 1 minute pickle in a solution of 5% MSA at RT. The electroplating current used was 1 A (2 minutes of plating=120 coulombs passed per experiment). The plated panels were washed with DI water and dried with hot air.

[0083] The formulations tested were:

[0084] a) The Ronastan TP acid tinplate system (Supplied by Shipley Ronal Corporation, Marlborough, Mass.) was used as a reference:

[0085] 15 g/l tin as Ronastan TP tin 300 concentrate (aqueous stannous methanesulfonate solution at 300 g/l as tin)

[0086] 30 ml/l Ronastan TP acid 70 (70% aqueous MSA)

[0087] 70 ml/l Ronastan TP-HCD Primary (a proprietary additive sold by Shipley Ronal (Marlborough, Mass.)

[0088] 15 ml/l Ronastan TP antioxidant (a proprietary additive sold by Shipley Ronal (Marlborough, Mass.)

[0089] 1.6 ml/l Ronastan TP-HCD secondary (a proprietary additive sold by Shipley Ronal (Marlborough, Mass.)

[0090] b) 15 g/l tin as Stannous Dithionate.

[0091] 30 ml/l Ronastan TP acid 70

[0092] 70 ml/l Ronastan TP-HCD Primary

[0093] 15 ml/l Ronastan TP antioxidant

[0094] 1.6 ml/l Ronastan TP-HCD secondary

[0095] c) 15 g/l tin as Mixed Dithionic Acid & Stannous Dithionate. The Free Acidity of the Solution was 0.5N.

[0096] 70 ml/l Ronastan TP-HCD Primary

[0097] 15 ml/l Ronastan TP antioxidant

[0098] 1.6 mil/l Ronastan TP-HCD secondary

[0099] d) Formula A)+1 g/l Sodium Dithionate

[0100] Visual analysis of the plated panels showed that formulas b), c) and d) allowed for an increased range of usable current density from 25-6 ASF to 30-2 ASF (47% improvement). XRF analysis of the plated panels revealed a 5% to 30% increase in electrodeposited tin thickness for the systems containing dithionate.

EXAMPLE 3

Acid Copper Electroplating

[0101] Several formulations were tested, and the results were compared through the analysis of electrodeposit quality (surface XRF and visual inspection). The formulations were prepared at room temperature and carbon treated. The electroplating experiments were performed in a 267 ml Hull Cell at RT with bright brass plated steel panels and moderate mechanical agitation. The panels were pre-treated by exposure to 40 ASF of cathodic current for two minutes in an alkaline phosphate solution at 60° C. followed by a 1 minute pickle in a solution of 5% MSA at RT. The electroplating current used was 3 A (100 seconds of plating=300 coulombs passed per experiment). The plated panels were washed with DI water and dried with hot air.

[0102] The formulations tested were:

[0103] a) Reference Formulation

[0104] 35 g/l copper as copper sulfate

[0105] 38.5 ml/l conc. sulfuric acid (96%)

[0106] 0.25 ml/l conc. HCl(aq)

[0107] b) Formulation a)+1 g/l ammonium dithionate

[0108] c) Formulation a)+5 g/l ammonium dithionate

[0109] d) 34 g/l copper as copper dithionate, 1N dithionic acid, 0.25 ml/l concentrated HCl

[0110] Analysis of the plated panels showed that formulas b), c) and d) give the best results allowing for an increase in the range of usable current density from 90-6 ASF to 120-3 ASF (40% improvement). The addition of ammonium dithionate allowed for the average cell voltage to be decreased by about 3%.

EXAMPLE 4

Enhanced Throw in Dithionic Acid Based Acid Copper Plating Solutions

[0111] Two acid copper electroplating solutions were made up identically except for the exchange of cupric dithionate for cupric sulfate and the exchange of dithionic acid for sulfuric acid. The Techni Copper U system additive (supplied by Technic, Inc. of Cranston, R.I.) was employed. The formulations were made up as follows:

[0112] [Cu ⁺² ]=24 g/L (A=cupric dithionate, B=cupric sulfate) as metal

[0113] [H ⁺ ]=2N (A=dithionic acid, B=sulfuric acid)

[0114] [Cl ⁻ ]=50 ppm

[0115] Additive=0.5% v/v Technic Copper U Additive (a proprietary copper plating additive sold by Technic, Inc. of Cranston, R.I. as part of the Copper U Circuit Board Plating System).

[0116] Brass plated steel Hull Cell panels were electroplated (standard pre-treatment) with copper at 12 ASF (amps per square foot) for 28 minutes (exactly 675 coulombs of charge was passed in each case). The panels were plated in a rectangular cell with the cathode positioned parallel to the anode. The cathode piece fit flush into the cell with no spaces around the edge. The thickness of copper plated on the front and back of the cathode piece were compared. The results are tabulated below; 1

[0117] The dithionic acid based copper electroplating solution had 67% better throw onto the back of the plated panel.

EXAMPLE 5

Nickel Electroplating

[0118] Several formulations were tested and the electroplating results were compared by visual inspection and by the analysis of electrodeposit stress using a deposit stress analyzer (1.2 in ² copper stress strips). The formulations were operated at 60° C. and were pre-treated with activated carbon. The nickel plating system was the Atotech Sulfamate Nickel Process provided by Atotech, Inc. of Rock Hill, S.C. The electroplating experiments were performed in a 500 ml beaker at 50° C. with air agitation. Two nickel anodes were placed on both sides of the test strip at about 1 inch distance. The stress strip panels were first treated for two minutes in a solution of 50% conc. HCl(aq) at room temperature followed by a DI water rinse. The electroplating current was 0.8 A (1 minute of plating=60 coulombs passed per experiment). The plated strips were washed with DI water and dried with hot air.

[0119] The formulas tested were:

[0120] a) Reference formulation: Sulfamate nickel formulation

[0121] 64 g/l Nickel as Nickel Sulfamate

[0122] 6 g/l NiCl ₂

[0123] 37.5 g/l Boric Acid

[0124] 5 g/l SN-1 Addition Agent* (Atotech, Rock Hill, S.C.)

[0125] 1.5 ml/l Antipit Y-17* (Atotech, Rock Hill, S.C.)

[0126] * Proprietary Ni plating additives sold by Atotech (Rock Hill, S.C.) as part of their Sulfamate Nickel Plating Process.

[0127] 2) 64 g/l Nickel as Nickel Dithionate

[0128] 6 g/l NiCl ₂

[0129] 37.5 g/l Boric Acid

[0130] 5 g/l SN-1 Addition Agent (Atotech, Rock Hill, S.C.)

[0131] 1.5 ml/l Antipit Y-17 (Atotech, Rock Hill, S.C.)

[0132] The stress analysis showed that formulation b) relative to formulation a) allowed for both a reduction in the tensile stress of about 4% and a reduction in the cell voltage of about 6%.

EXAMPLE 6

Ferrous Alloy Cleaning

[0133] Aqueous solutions of ammonium sulfate and ammonium dithionate were compared for rust removal. Both solutions were prepared by dissolving 5 g of the corresponding salt in 100 ml of DI water at room temperature. Two identical pieces of rusted steel were prepared. One piece of rusted steel was submerged in the sulfate solution while the other piece was submerged in the dithionate solution. Rust removal was monitored as a function of time. The ammonium sulfate solution removes very little rust even after 4 days, while the aqueous dithionate Solution removes a significant amount of rust within one hour.