stanous says gold is present but smb not dropping it.

[watcher6880]

I recently did a batch of fingers using the AP process and ended up having to recover gold with a piece of copper sheeting strip in the form of black powder. I washed the powders with hcl and then dillute. Repeated until clear. Let them dry and put it through the process again to get rid of as much base metal and trash as possible. I then dropped my clorox to dissolve the gold leaving a grayish shiny crystal saltlike precipitate that floated at the top as gold dissolved. This I assume is cemented silver. Which I now have in my stock pot with the rest of my filters. I then tested solution with stanous and came back purple so I added 3 times water (distilled of course lol) to my 1 part solution of auric chloride. Then dropped in almost a half cup of smb, stirring it (solution is roughly close to 950ml with water. Figuring 28gr of smb to 475ml). I waited 2 days. Nothing happened. Solution still golden in color so today I am heating solution on a hotplate. Very fine bubbles simmering. I see what looks like microscopic hairs or specks suspended in solution. So far no precipitate dropping after two hours of heating. what's next? I seem like I missed something somewhere. Hokes has been a great help so far but after going back I can't seem to track down my problem. Am I adding too little or too much smb . Should I NOT stir it after I pour it in?

 

[philddreamer]

Wow! Half a cup of SMB... How much gold did you dissolve? The ratio of SMB is 1:1 to gold expected. You may add a bit more, in case there's any free nitric or any clorox present. If you heated the solution & got rid of the clorox you should have had a drop...

From what I understand, I would add some water, then evaporate to syrup; add some HCl & proceed with the precipitating process.

I hope this time it works for you.

Phil

 

[vegaswinner]

I then tested solution with stanous and came back purple so I added 3 times water (distilled of course lol) to my 1 part solution of auric chloride. Then dropped in almost a half cup of smb, stirring it (solution is roughly close to 950ml with water. Figuring 28gr of smb to 475ml). I waited 2 days

After dissolving with chlorox did you wait at least 24hrs for the chlorine to dissipate before adding your smb? If not the gold wont drop as the smb is fighting the chlorine.

If 2 days has past then the chlorine will now be gone and I would just add the 1.1 ratio of smb again and it should drop (1g smb will precipitate 1g of gold).

 

[lazersteve]

Are you sure your SMB has not gone bad?

I have found that if it clumps up due to moisture it is not as effective as when it is free flowing.

What is your source of SMB (stump out or lab grade SMB)? SOme stump out is potassium nitrate, not SMB. You'll need the Bonide brand for SMB.

If your SMB is good, then evaporate the solution down gto half of it's original volume and try preciptating from a more concnetrated solution.

Steve

 

[Lobby]

If you have a home brewing store close by, you can get SMB from them. They normally sell it in 2 oz or 8 oz (1/2 pound) packets. It's used in winemaking. Salesman was very curious when I bought 8, half pound packets. :mrgreen:

When I was having trouble with my initial batch of SMB (which I'd bought at a science store), I switched back to copperas and all was good. That early batch of SMB was lumpy, just as LazerSteve warns about. Since I've got the new SMB all is good.

I still think I get more complete drops with copperas. With SMB, even if I leave it in contact with the dropped gold overnight, when I wash the gold powder with HCl to clean it, I end up with gold in the HCl wash, which I have to drop again. With copperas, that doesn't happen to me.

But you didn't ask about that... :mrgreen:

 

[watcher6880]

Back on this. I'm evaporating the solution down and starting from that. I am getting a flaky light substance in the solution. Hoping this is not foreign material since I filtered all of that out before I dissolved the black powder. Also what leads me to think this is because as my solution evaporates it is turning greener and greener in color than the original golden yellow it started out with.

 

[Geo]

thats not uncommon when evaporating. from your first post, the shiny silver looking crystals is probably lead so it wasnt as clean as you had hoped it was. i would bet on copper being there too. dont despair because its nothing that cant be fixed. the flaky material you see now is more than likely salt from the half cup of SMB. if you started with 1000 ml's of solution, render it down to half the volume and let it cool completely. filter out all solids and test with stannous. if it is positive, do not dilute. add a teaspoon of SMB and stir. if you dont see a dramatic color change, do worry. just let it sit overnight and check it in the morning. test with stannous before you do anything else. if it is still positive, add another spoon full and stir. repeat until its a negative. it will need to be refined again. this time you can dry the powder and weigh it, that way you will know exactly how much SMB to add.

 

[Moo]

Salesman was very curious when I bought 8, half pound packets. :mrgreen:

rofl wonder what he was thinking, probably would have charged double price if he knew what you wanted it for :mrgreen:

 

[kjavanb123]

Hi,

I just had a very similar problem, you could use zinc addition as your last resort if you are dealing with a large volume AR solution. You can read my post in the "Type of Scrap" section if you want more detail on it.

Regards,
Kevin