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Anodic Dissolution of Gold Using a Packed Bed Electrode

IP.com Disclosure Number: IPCOM000083807D
Original Publication Date: 1975-Jul-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Horkans, WJ: AUTHOR [+2]

Abstract

A gold (Au) plating solution requires a soluble form of Au. Au dissolves at anodic potentials in Cl/-/ solution, with the rate of dissolution increasing with higher Cl/-/ concentration and lower pH values, but the rate is insufficient for practical application. When the anode is composed of finely divided Au powder, the greatly increased surface area provided permits a higher total current to be used with a relatively low-anode potential. No O(2) formation occurs.

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Anodic Dissolution of Gold Using a Packed Bed Electrode

A gold (Au) plating solution requires a soluble form of Au. Au dissolves at anodic potentials in Cl/-/ solution, with the rate of dissolution increasing with higher Cl/-/ concentration and lower pH values, but the rate is insufficient for practical application. When the anode is composed of finely divided Au powder, the greatly increased surface area provided permits a higher total current to be used with a relatively low-anode potential. No O(2) formation occurs.

The figure shows a small-scale batch apparatus for dissolving Au in concentrated HCl.. A loop 10 of gold wire 14, which is exposed, is set on a porous glass fritted disc 11 formed in funnel 12. Above and about loop 10 are Au powder, mesh, bundles of wire, sponge particles, or foil bits 20 held down by clean glass wool 13. The funnel 12 is filled at the top with concentrated HCl. Wire 14 is protected from attack by HCl above the loop 10 by insulating material
15.

Electrode chamber 16 contains electrode 17 and has a porous glass frit separator 18 and is filled with concentrated HCl. Hydrogen ions pass to negative electrode 17 and Au ions pass into solution from Au 20, and drip in drops 21 down into solution 22 in container 23. The solution 22 can be put into funnel 12 again in order to convert all of the chloride ions into an AuCl complex, which eliminates most of the H/+/ions from solution.

There are other arrangements in which a packed Au anode can...