plating, anodizing, & finishing Q&As since 1989
How to Make Sodium Gold Thiosulfate
October 10, 2012
Q. I am a MSc student in the field of electroplating. My MSc thesis is about Sodium Gold thiosulfate electrolyzing. As the first step I have made Gold Fulminate (as 1 gr Au). Now I want to make Sodium Gold thiosulfate complex. My questions are listed below:
1. What is the detail of the formation's reactions complexing?
2. How much Sodium thiosulfate should I add to the Fuliminate in order to make the Sodium Gold thiosulfate complex?
3. What is the condition of adding Sodium thiosulfate to the solution?
I want to appreciate your kindness.
A. Hi Hooman
My first advice is to strongly advise that you find a safe way of disposing of your gold fulminate. It is a powerful and very sensitive explosive even when wet.
As a general rule you should never attempt any preparation without full knowledge of the properties of both reactants and products and a plan to dispose if any waste.
Gold thiosulphate is prepared by adding (slowly and with constant stirring) a solution of tetrachloroauric(lll)acid (gold chloride) to a slight excess of sodium thiosulphate [affil link] solution. Some sulphur dioxide is given off. Filter off any sulphur precipitated and add absolute ethanol to precipitate the pure salt.
At MSc level you should be able to calculate the quantities for yourself.
I am not aware that the thiosulphate has been used for plating although gold sulphite has been used commercially for many years. It has excellent throwing power but is not very stable and the deposit is too soft for many applications.
October 16, 2012
First of all, I want to appreciate your kind reply.
Q. Then I have 3 questions listed below:
1. Would you please suggest me some references including journal articles, handbooks, etc., in the field of sodium gold thiosulfate? I found a lot of articles in this field but they don't include any detail of the mechanism.
2. Is it possible for you to mention the reactions of sodium gold thiosulfate complexing from fulminate step?
3. Finally, I want to know the temperature and pH required for making sodium gold thiosulfate from HAuCl4.
I would really appreciate your time and concern.