Still learning and need some reassurance

[gold4mike]

I have inherited roughly 20 gallons of AR in which many gold bearing computer parts have been dissolved. I started by filtering everything through double coffee filters to catch the sludge and skeletons of parts. I picked out and rinsed the items that were undissolved. There was no remaining undissolved metal visible whatsoever.

My initial assumption is that, since there are no visible metals, much of the gold will be in the sludge recovered from the bottom of the buckets, and some will still be in the liquid as well.

I tested the liquid with Stannous Chloride and did get a positive test result.

I decided to evaporate the solution down to reduce volume and to drive off any remaining nitric. This method was soon abandoned due to the formation of lots of crystals. The crystals will dissolve in water and I believe them to be Copper Chloride.

I then took the advice I have seen given on the forum many times when a noob has "nuked" everything in AR and hung a piece of copper bus bar in a 4 liter beaker full of the filtered AR. After roughly 4 hours of cementation I tested the liquid and believe all PM's have dropped.

A picture of my before and after Stannous Chloride tests is below.

Am I correct in my assumption that the AR is now barren of PM's and I can safely siphon, filter and relegate the liquid to my nitric stockpot?

 

[Palladium]

Personally I’m not sure how long it takes completely cement a solution, but i usually give it a couple of days. Stir occasionally. I'm not sure 4 hours would do it. I could be wrong though. If you do miss a little bit it should be recovered in your stock pot anyways.

 

[qst42know]

I would guess it to be dependent on the surface area of copper exposed to the solution, and the amount of agitation. I use an air pump and a length of glass tube to keep the solution moving.

What may help to keep values out of the stock pot. I tried something the last time. I added SMB to a cold solution and allowed it to precipitate. When the gold was on the bottom and a negative stannous test the solution still had a faint brown tint. When I have had time this tint will settle in a day or two. Instead I then brought the solution to a brief boil. The SO2 odor was gone, nothing was floating, and the solution was crystal clear. The gold was well clumped It was easy to pour off all the solution.

The gold powder seemed to act as seed points for the boil so the solution filtered itself.

 

[gold4mike]

I've noticed similar clumping when cleaning gold powder with a HCl boil. I'll have to give that a try tomorrow with the siphoned-off liquid and see if anything else settles out.

I have another 4 liters cementing overnight. I'll compare the amount of dropped powder between the two tomorrow.

I thought I was on the right track, thank you for your input!

 

[samuel-a]

Am I correct in my assumption that the AR is now barren of PM's and I can safely siphon, filter and relegate the liquid to my nitric stockpot?

Seems like it from where i'm sitting.

When i'm not sure about a stannous test, i perform it both in a spot and on a q-tip/filter paper.