Dissolved my gold in boiling HCl

[AndrewSuperD]

I used a large Vlassic pickle jar to hold my gold rinse water after some gold drops. There was a layer of fluffy grey/black on bottom of jar after two weeks. I evaporated off with bun coffee pot burner over the course of three days till down to about 300ml and all the sediment. I filtered out with funnel, cotton ball, and filter paper. All the black sediment was in the filter and cotton ball. I boiled filters and sediment in 200ml HCl for about 20 minutes. Solution turned really dark brown or black maybe. Filtered again with filter paper and cotton ball. Put cotton ball, darkened filter, and sediment ( not much) in 100ml HCl and about 2ml nitric for about 30 minutes( No colored vapors. ) and then added Sulfamic acid at about 93C. Almost had a boil over. Sulfamic reaction stopped. Cotton filtered again. Crystal clear yellow. Pictures below. Stannous test showed nothing. I was like “What?????” I didn’t expect much, but there was heavier sediment in the bottom of the coffee pot so I thought I had something. Tested the filtered solution from first HCl boil. This solution was very diluted because I had just washed the glass before filtering into it, and didn’t bother to dump all the clean water out. Pictures below. A little color developed on the paper after a while. I’m I assume I dissolved my little bit of left over wash water gold with boiling HCl. In summary, the yellow liquid after Sulfamic showed absolutely no color after Stannous test. The original HCl boil filtered and put in the disposal jar developed some color on Stannous test. The two left papers are two tests of the original HCl boil liquid and the far right on is a test with a known test solution (just to make sure Stannous is good). Thoughts?

 

[nickvc]

HCl will dissolve some gold as it will absorb some oxygen from the atmosphere and it can also depend on what else has been dissolved if just doing recovery processes, this is why we have the stockpot.

 

[AndrewSuperD]

Very good. Thank you. To the stock pot it goes! This morning, all my papers from the Stannous test have definitive purple stains. I can assume gold in almost every beaker in minute amounts. I guess, I will just combine it all and evaporate it down then add it to the stock pot. Roughly, 600 mL in all. Thank you very much for your reply.

 

[AndrewSuperD]

Since I have several hundred milliliters of solutions (gold wash, HCl bath, AR+Sulfamic) that are stockpot bound, I decided to pour the multiple jars of solutions, that I was keeping separated as I thought one of them would contain some gold, all into the same coffee pot to evaporate. I will then test with Stannous and dump the lower volume liquid into the stock pot. As I pour out the liquid from the smaller beaker that I show above (AR+Sulfamic), I see residue that seems to have adhered to or cemented out to the glass. Pictures are below. Has this happened to anyone else? Looks like gold, but how could that be? The maximum heat that particular solution reached was 97°C per my infrared thermometer while I was adding the Sulfamic acid, and the coolest it would have reached was around 3°C. The beaker was washed and clean and dry before I cotton filtered the AR into it. Any thoughts, and next step ideas, are greatly appreciated.

 

[FrugalRefiner]

Looks like you forgot the pictures.

Dave

 

[AndrewSuperD]

 

[dpgold]

Since I have several hundred milliliters of solutions (gold wash, HCl bath, AR+Sulfamic) that are stockpot bound, I decided to pour the multiple jars of solutions, that I was keeping separated as I thought one of them would contain some gold, all into the same coffee pot to evaporate. I will then test with Stannous and dump the lower volume liquid into the stock pot. As I pour out the liquid from the smaller beaker that I show above (AR+Sulfamic), I see residue that seems to have adhered to or cemented out to the glass. Pictures are below. Has this happened to anyone else? Looks like gold, but how could that be? The maximum heat that particular solution reached was 97°C per my infrared thermometer while I was adding the Sulfamic acid, and the coolest it would have reached was around 3°C. The beaker was washed and clean and dry before I cotton filtered the AR into it. Any thoughts, and next step ideas, are greatly appreciated.

I had gold clinging to walls of plastic and glass alike, it would not come off with any rinsing or spray. It would come off if you wipe it with a piece of filter and/or dissolve off with AR and then spray rinse the walls.

 

[Martijn]

Invisible dirt on the glass surface will make the fine floating freshly precipitated gold stick to the walls.
Clean the beakers better before precipitation.
Wipe it off with a piece of paper towel and throw that in the melt or second digestion.
Or use that beaker for the washing steps to get pure shining gold, you may clean the entire beaker along with the gold.

This also demonstrates perfectly why you should never touch chemical beakers without gloves.. There is invisible 'dirt' on everything. And with dirt, I'm meaning toxic chemical salts and more.
It may look clean, but it will hurt you in time.

Martijn.

 

[Shark]

Invisible dirt on the glass surface will make the fine floating freshly precipitated gold stick to the walls.
Clean the beakers better before precipitation.
Wipe it off with a piece of paper towel and throw that in the melt or second digestion.
Or use that beaker for the washing steps to get pure shining gold, you may clean the entire beaker along with the gold

Also, you can do a tiny amount of AR and clean the glass. Then rinse it into your stock pot since it is a very small amount of gold. Recover it later with your other waste.

Good, clean glass is easier to work with.