Gold precip. is orange in color

[donl001]

Gentlemen,

I have a odd situation that I have never experienced. I am refining gold from a batch of approx. 95% gold filled jewelry. The remaining material is some plated items. I disolved the base metals with the normal 50% nitric acid solution. After the reaction was complete, I brought the solution to a rapid boil for approx. 30 minutes. I then diluted the solution with 3x tap water. I noted that the gold was a reddish brown at this point, but, not particularly unusual in color. I allowed the solution to settle over night and when I observed the solution the next day, the dropped gold had turned a bright orange in color. The solution containing the base metals was a normal greenish blue. I suspect that there maybe something in the tap water that could have caused this issue, but, I have used the same process numerous times and have never observed this situation before. Has anyone else ever experienced this or any thoughts on the cause ? Also, do you feel that it ok to continue to process the orange gold?

Thanks in advance for any assistance!!

Kevin

 

[machiavelli976]

kevin, there is something missing in your thread.i see no refferences about AR . nitric digest only base metals and some poor stainless steel. have you rinsed the gold foils before AR digestion? i am not used with this kind of corner cutting like dropping gold along with base metals in solution. what should be your gold purity ?

 

[Platdigger]

machiavelli976,
I believe what Kevin is saying here is that this "orange" gold is what is left after the nitric digestion.
I also believe the reason he said after the "drop" was just that there was fine particals of gold in suspension that he had to wait to settle.

 

[donl001]

Sorry for the confusion, but, Platdigger is correct. The gold that I am refering to is the gold left after the initial digestion of the base metals in nitric acid. I am still at the dilution stage of the nitrate solution remaining after the 1st digestion. After dilution with tap water, the remaining gold turned a bright orange....Any suggestions?

Thank you!!

 

[Harold_V]

It's entirely possible that the color you see is nothing more than virtually pure gold. When you precipitate from concentrated and clean solutions, the precipitate comes down a color that is closely related to the color of ground cinnamon. Likewise, if you happen to hit on a good percentage of gold to base metal/silver, after processing by nitric, the remains often are a nice bronze color.

Right now I don't see anything wrong, but I may not understand everything you've tried to say. Personally, I'd rinse the solids until the rinse water was clear, then I'd dissolve, evaporate and filter, in preparation for precipitation.

One comment. I think the vast majority of these guys process only with ambient temperatures. That will almost always yield different results than that achieved by boiling. I, like you, processed with heat---ALWAYS. I couldn't afford the luxury of starting a lot of gold and allowing it to work on it's own schedule. Forced heating cuts, by a huge margin, the amount of time spent on any given lot.

Harold

 

[donl001]

Thank you Harold, once again I believe that you have hit the nail on the head!

Last evening I siphoned the majority of the solution off and proceeded with a tap water rinse. The appearance of the gold seemed to be somewhat subdued from the initial bright orange coloration. I will re-post my results after I complete the rinsing stage.

Thanks once again for all of the assistance that this board and it's members provide.

Kevin

 

[donl001]

Gentlemen,

All is well!!! I washed the gold with several rinses of tap water and processed the remaining gold with A/R. The auric acid was a normal yellow. Thank you for your assiatance!!

Kevin