AR troubleshooting - please advise!

[evanJ]

The original source was karat gold which was inquarted with silver and copper to about 5.25 karat (I explain this mistake in another thread)
I did 3 room temp nitric baths until the solution was almost clear. What follows are my AR processes & questions. Thanks!

I left my AR with about 28 grams of gold (30ish grams overall solids) overnight in AR, and woke up to a greenish solution with a bit of black powder and a bit of white powder at the bottom. It tests positive with stannous.

My assumption is that the green indicates copper, which may precipitate along with gold during SMB, and that this means I should do final bath (or two) in nitric once I'm done with everything else.

The black I'm assuming is gold that didn't dissolve, because when I added a heating element and a little bit of fresh AR it almost all dissolved.
(note: I'm not being precious with my nitric because I already am planning to do a nitric bath at the end, so I don't mind a bit of free nitric at this stage.)

The white/greyish/purplish powder I'm assuming is silver chloride, some of which reacted to UV light outside. I filtered this off and added to my silver chloride waste jar.

So!

• Question 1: do the above assumptions check out? (green AR = copper, good way to get rid of it is to do a final wash of my SMB precipitates in nitric)
• Question 2: Is it reasonable to put all of my silver chloride in another AR solution and check for gold? If I lost a lot of gold, I expect it's hiding in my silver chloride.
• Question 3: My AR is performing pretty slow at room temp, and a bit too intense over low heat. Enough that it's hard to escape at least a faint chlorine smell, and it makes me want to completely avoid the area and hold my breath while turning off the heat source... Is there an easy way to find a happy medium?
• Question 4: I prepared a small amount of AR for .5 grams of 24K gold I had, which I hoped to use as a control so I could test my stannous, practice precipitating with SMB, etc. But this gold is taking FOREVER to completely dissolve. I got enough into solution for testing purposes... Can I remove the remaining chunk and wash in distilled water and then just treat as 24K again?

Thanks all for all your help so far!
I am trying to limit my posts to things I can't find in the archives, and a lot of older threads have been hugely helpful.
Sorry if some of these questions have been asked before.

 

[4metals]

I think the one improvement you can make is to heat the inquarted digestions. With 2 digestions, the first being 2 parts distilled water and I part conc (68%). Nitric and the second boil being 50-50 distilled to nitric. This should yield a 99+% Gold insoluble and when you digest it in aqua regia, a beautiful red solution awaits. You will be chasing around minute quantities of Silver because your cold parting just didn’t penetrate sufficiently.

Heat really helps and having a hood does as well. Until then always leave enough room in a beaker for the reaction to rise 100% without overflowing. Then set your heat for a low boil and back off. When the acid has no more metal to digest, the blowing of red fumes drops off. You could control what you inhale by controlling the heat with a long extension cord on your hot plate so you can unplug, and therefore cool, from a safe distance.

 

[evanJ]

Thank you! It sounds like nothing else in my methodology set off alarm bells, which I'm glad for.
You were right in your response on my other thread by the way - the original inquartation should have been redone.

I think the main issue was that one of my batches didn't 100% mix in the crucible, and so some areas were gold heavy and couldn't let the nitric do its job.

I'm thinking that would explain this coloration for my AR (after adding about 100 ml distilled water)
Look how red it is! lol.

Thank you again for your advice here and elsewhere