Precipitating with hydroquinone

[NobleMetalWorks]

I have been using hydroquinone to precipitate Au for awhile now. I recently had an interesting precipitation I wanted to share.

I precipitated like I normally do, waited and checked with Stannous, the test was positive so I added a little more hydropquinone, then quit for the night. I got up this morning, checked on some solutions that are at different stages, and found something that looked like a mushroom on the top of the solution I precipitated with hydroquinone.

Mushroom like structure

I have never seen this before. I wasn't even sure that it wasn't something that fell into solution, so I took a few pictures before I went further. I checked the bottom, the amount of precipitant looks to be a lot more than what I dissolved into solution, it's really spongy and collapses when stirred just a tiny bit.

Looking at the floating mass on the top, I thought that something weird happened, but this was just AR and gold that had already been refined once. So I know there isn't anything weird in solution, looking at the bottom of the mass, I could see crystals of gold hanging down.

So the mass that looks like a mushroom from the top, is actually a mass of gold crystals on the bottom that have grown down into the solution. I have never even heard of anything like this before. When I poked at it with a glass stir rod it broke apart and fell to the bottom right away. All the sponge fell to the bottom and compressed someone and now looks more like what I was expecting. But I have no idea what exactly happened, or how the Au was able to precipitate in that way. Does anyone have any idea? It's totally stumped me. I am not worried about the Au, I can see it, I am just really curious how it was able to precipitate in the way it did.

Scott

 

[Lou]

Probably didn't stir it in.

 

[NobleMetalWorks]

Hahaha,

You are right Lou...

Yeah, actually I figured it out later... That's exactly what I did and I have re-created it since.

It's the film that coats the top when you first put hydroquinone in solution, gases were caught underneath which allowed it to stay floating, the edges because heavy and curled under because the air tended to stay in the center. It's interesting the way it developed.

At the time I put the hydroquinone in, I had a phone call that ended up being a few hours, this was late at night anyway. So I added it, stirred a little then left the solution to get the phone call, and didn't check it again until morning. And as you probably already know Lou, if you don't stir hydroquinone into solution really well, it will float right back up to the top and make that metallic looking coating on the surface again.

When I first saw it however, it was so unusual, and I was so curious I had to post it. If I waited a day, I probably wouldn't have posted it because I was fairly sure what I did and it wasn't nearly as interesting after I realized how simple the reason was for it turning out how it did. Still interesting though, later when and if I ever have any free time, I might try to take a time lapse video of this reaction and results.

Scott

 

[Lou]

I guessed that was the case.

Seeing your photo it reminded me of something.
When I was in college, I used to dissolve a compound that I wanted to purify in a solvent in which it was highly soluble. Then I'd slowly run a solvent of opposing polarity down the sides of the flask and let it cool. Typically, I trickled light ligroin or petroleum ether into heavier chloroform or ethyl acetate. Large crystals would grow as the phases intermingled and changed the degree of saturation. It was slow growth from diffusion/Brownian motion. I'd have to bust them off the walls.

Good times.

 

[NobleMetalWorks]

When I owned a nightclub, I used to bartender for fun. I had a whole serious of drinks I made, that I dreamed up myself. Some alcohol is heavier than others, so I would pour against a cherry and let the alcohol run along the inside of the glass, so that I could take advantage of the different weights and surface tensions and end up sometimes with 5 different layers in a pint glass, of different alcohols. Any good bartender can do it if they can hold a bottle steady.

Sometimes my resulting solutions remind me of drinks I used to make, the way they react, how they stratify, the colors. It's all good fun.

Scott