AuCl3 in solution forming a precipitate

[luisfran]

Hello,

I am dissolving solid AuCl3 in water to obtain the Au3+ ions in solution. After I add the water and agitate a little, a precipitate appears; first the particles are of a clear color and after a few minutes they turn dark. Do you know what is it? and how can I avoid it?

Regards,
Paco

 

[4metals]

Gold chloride is not one of those reagents you see every day in powdered form, are you sure it is gold chloride and not some other powdered gold salt? If you are sure, it is soluble in water to about 68 grams per 100 ml, you may have added in excess of this and that would explain why it did not all stay in solution. I haven't seen any gold chloride in crystalline form in many years but I do not remember it being clear crystals. Please, for your own safety, be sure of what you have.

Gold potassium cyanide is a commonly found gold salt, please don't mistake the two!

 

[luisfran]

Hi thanks for the help!

I am sure is gold chloride (It comes from a chemical manufacturer company and it is 99.9% pure), I also use distilled water and teflon to handle the gold chloride in order to avoid that it reacts with the metal instruments. Also the concentration I am using is way below the solubility limit of AuCl3 (I am using less than a gram in 20 ml).

I was thinking maybe Au(OH)3 was precipitating but since I am using distilled water it doesn't make much sense, what do you think?

Best,
Paco

 

[Lino1406]

What precipitated is simply gold, by a
presence of any reducing agent in solution.
Remember gold ions are strong oxidizers