Creamy-coffee colored suspension appears when washing silver metal powder

[Geber]

If someone could tell me what in God's name this is and how to fix it that would be greatly appreciated.

This was my first jewelry sweeps refine. I burned them with a torch until they wouldn't smoke. I dissolved them in hot dilute nitric acid. I filtered the solution in a Buchner funnel with a medium filter paper and set any solids aside. The solution looked very clean and blue. I added HCl and got some nice AgCl. This I washed many times with hot distilled water until it failed an ammonia test. Then I converted to Ag2O with lye. The Ag2O had an unusually light brown color that I had never seen before. It usually looks almost black when I do it. Even still, it was homogeneous looking and extra lye did not make it darker. Then I added some glycerin with water to reduce it. I stirred it and it never got very hot. The beaker became mirrored and then the mirroring went away and it looked like all the metal was completely reduced, some 150 g.

I resolved to wash it until the water had a neutral pH because I wanted to see if getting rid of the NaOH would make a noticeably purer silver`. It was somewhere like 13-14 and took many many washes with distilled water, heated to steaming temperature. Every two washes, I tested the pH with strips. As it got to 8, and then seven, the COFFEE color appeared. Adding distilled water, which was clear, caused the coffee color when it hit the silver. All the previous washes did not do this, but once the coffee appeared, every wash after that caused it to reappear. It is now sitting in the coffee-colored liquid (hopefully it will be ok tomorrow).

A few caveats: I distill my water with a Vevor water distiller. I use water that is filtered, but has some oxides suspended in it, but it comes out clear. I'm pretty sure the same batch of water was seen causing the coffee color and being clear on the silver. Before the color appeared, the silver behaved very well in terms of sinking down, like gold in a gold pan, and was easy to decant. When the coffee color appeared, it seemed to want to float on top more. I think it is a suspension or colloid, not a solution because it is opaque. Finally I would add that this color, or something similar, but more green, appeared when I first added the glycerin water. Is it silver? Should I try to wash it all off? Will I lose silver? Please help.

Thank you

 

[4metals]

First off Ag₂O is always black or very dark brown. The mud you showed I assume was the result of filtering out the solids after you treated the Silver Chloride with lye. Bottom left image. It actually looks more like what the Silver metal looks like after reduction. Are you sure the lye you used had no additives? I am a bit spoiled having always used bulk reagents for processing and the Silver Chlorides always came out black and uniform. So the first question was the lys just sodium hydroxide or were there additives?

Second did you reduce the oxides with glycerine? I am not familiar with that process as I always used sugar or corn syrup. If you did mean glycerine what was the process you followed?

 

[Geber]

First off Ag₂O is always black or very dark brown.

I should have taken a picture of the silver oxide. It had to be silver oxide... It's what I got when I added the lye to the AgCl.

The mud you showed I assume was the result of filtering out the solids after you treated the Silver Chloride with lye.

All three of those pictures with the mud - that's silver metal after reduction. It looked totally normal until the pH got to around neutral. Then the creamy coffee color appeared.

I didn't filter anything after treating the AgCl with lye. I left in the beaker and reduced it.

Are you sure the lye you used had no additives?

Yes. It says 99+%.

Second did you reduce the oxides with glycerine? I am not familiar with that process as I always used sugar or corn syrup. If you did mean glycerine what was the process you followed?

Yes I reduced the oxides with glycerin. It's the same as sugar/corn syrup. I added a mixture of glycerin and water to the silver oxide and stirred it in.

 

[4metals]

I started using the caustic corn syrup method in the 1970's when Silver was $4 an ounce so more a nuisance than it was worth. So I used corn syrup because it was, and still is, cheaper than glycerin.

You said the original material was jewelers sweeps. Were there any brushes and buffs in there before you burned them? Brushes often have lead hubs and can generate sweeps loaded with lead. Lead is soluble in nitric acid and will drop out of solution with Hydrochloric Acid along with Silver. Is it possible that a percentage of your white chlorides were partially lead chloride. Lead chloride is soluble in hot water and Silver Chloride is not (or much much less soluble than lead chloride). Did you boil the chlorides to assure no lead chloride was in the mix?

I may be grasping at straws here but lead may be a part of the problem.