Surface Tension Floating Gold

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nicknitro

Well-known member
Joined
Jan 10, 2009
Messages
320
Location
United States
Hello All,

In my past few precipitations of gold from AR , and HCL/CL solutions using SMB, I have noticed that the surface tension of the water/dilute acids seems to hold some of the gold on top of the solution. This is kinda a pain when refining small-scale amounts of gold "5-10" grams.

Is it the natural surface tension holding the fine gold out of solution, or has my housekeeping been less than desireable again, and some oils have gotten into my solution?

I still have a nice layer of brown-mud precip. , it's just frustrating to miss some of the gold especially when dealing with e-scrap.

P.S. the AR solution was a test solution using pure gold and AR, then just water and SMB. No urea as the AR was saturated with gold.

Thanks for the advice,
Nick
 
Harold will tell you incineration is key, and he is right.

But even following that there are times that somehow you get oils in your solution, it does not take much. I just put the smallest dab of liquid dish soap on the end of a glass stir rod and touch it to the surface of the solution. If any gold is still on the surface tap it down with the glass rod, it will settle rapidly.

Edit; spelling
 
Nick,

No problem, but it caused me to re-read your original post. Are you saying you did not de-noxx because your AR solution was saturated with gold?
 
Oz,

No I did not denoxx, as far as URea. There was still a good chunk of gold not dissolving in the AR solution. Again, this was a small scale test. The AR solution was a bright deep yellow , and when SMB and water was added no fizzle was apparent.

Nick
 
nicknitro said:
Oz,

No I did not denoxx, as far as URea. There was still a good chunk of gold not dissolving in the AR solution.
Click to expand...
It's important that you provide some free HCl when you use added gold to consume excessive nitric. Action will cease the moment either of them is depleted.

Gold will precipitate to some degree when there is free nitric, although it must be in very low levels of concentration. It creates problems when you wash, however, so insure that you do eliminate all of it.

In order for gold to not float, you must carefully wash your glassware before using it for precipitation. Avoid handling with bare hands unless they have just come from the wash water and have been washed and rinsed well. If your glassware is stained, clean it with AR, or clean it with Bon Ami and a sponge. It should be spotless and free from scratching if you expect a clean precipitation that will settle readily. If you find a trace floats, shoot it down with a wash bottle.

Harold
 
Harold,

Sometimes when I am done with my washes I seem to get a white salt that forms when the washed gold is being forced dry. If I add water and boil it again two or three times, it seems to go away.

Any idea what that white salt would be. I wonder sometimes if I am using too much ammonia hydroxide during the washes?

Thanks!
 
Ammonium hydroxide isn't likely the source. If it is, continued heating will evaporate the white material.

When doing the ammonium hydroxide wash, If you heat it, it doesn't take long for the ammonia to be discharged (remember-----it's just dissolved in water). Notice that if you boil the material for a short period of time, the smell is gone?

I used tap water for all of my washes and rinses. I expected traces of materials to form, but they do no harm unless they are metallic in nature. Considering my end product was very good, I wasn't the least bit concerned about the traces of what I call "hardness" that remained with the gold. Melting eliminated it completely, at least as far as I could determine.

If you are using distilled water, I'm at a loss to explain what you're seeing, but keep in mind, the wash cycle is prolonged because the gold doesn't necessarily get fully exposed to the washing cycles. Some of the minute particles of gold may have traces of solution entrapped such that it can't be washed out easily, if at all. That's the reason I did long, hard boils in my washing sequences, and is also the reason I refined my gold twice. If the solution is relatively clean, even if some gets trapped, it will not be a significant contaminant. A second refining really pays dividends.

In the end, some traces are never removed. I would consider that, perhaps, that is the source of some of the residual salts you see.

Harold
 
Melting the gold after washing with ammonia is very smart. Any halogen impurities (as well as others) are volatilized away. Great way to remove any junk from tap water that is present in gold.
 
glorycloud said:
Sometimes when I am done with my washes I seem to get a white salt that forms when the washed gold is being forced dry. If I add water and boil it again two or three times, it seems to go away.
Click to expand...


Depending on your wash techniques it could be lead chloride. Your ammonia will catch small amounts of silver chloride and wash it free, boiling water will do the same for the lead chloride.
 
I have been doing three series of washes with first HCL, then water and them ammonium hydroxide. I then seem to have to do another couple of washes with water due to the small amount of white salts that form right when the last bit of water is drying off of the gold in the coffee pot.

I should be trying Steve's new mini furnace later this week with some gold powder. I will post some pic's. :)

thanks again!
 
Harold,

Thanks as always, you have opened my eyes. I really have to work more on my housekeeping discipline. That may be my biggest flaw, in my whole refining experience.

At any rate thanks all, I will keep in mind next time with AR the HCL trick, as I should have excess gold to use to rid the noxx. Just remember, weigh in weigh out.

Nick
 

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