Filtering and Adhesion

[cbarney522]

Hi All,

After a year of study and preparation, I started refining a few months ago. So far, I've accumulated 10 gr of gold from computer parts, gold-plated metalware, and gold-filled jewelry. I've had success using two different Aqua Regia (AR) methods, as described elsewhere on this forum:

method #1: boil the pregnant AR down to nearly a crystal, reconstitute with HCl, repeat several times. This eliminates the nitric, and when adding the Sodium Metabisulfite (SMB) the precipitation is immediate and dramatic. On one of my batches, the entire solution turned brown in half a second.

method #2: mix hot water with Urea until dissolved, and then add to pregnant AR until fizzing stops. The fizzing is not noticeable. I have to hold it up to the bright sky to see the tiny bubbles. After an hour or so, it stops. Then I drop the gold using SMB. It takes a long time - 24 hours minimum.

I have three questions for the more experienced members of this forum.

question #1: which method is superior? The AR boil-down method is slower, but the gold drops faster and is easier to deal with. It's fairly course and filters easily. The AR Urea method is faster, but the gold drops really slowly, and is hard to deal with. The gold is extremely fine, sticks to the sides of the jar, and much of it passes right through my filters. I feel like I'm losing gold using the AR Urea method.

question #2: are there any filters that can filter out the extremely fine gold that precipitates after the AR Urea method? I've tried coffee filters and 11-micron LabNerd filters. It catches a lot of the gold, but not all. I'd estimate 20% is fine enough to pass straight through the filter. And the filter ends up impregnated with the gold as well, and doesn't completely rinse out.

question #3: I am having problems with gold adhesion on glass. I have to scrub my glassware with a small brush to get the gold off. What a pain. What is causing this? The glassware was thoroughly cleaned prior to use. I only use distilled water.

 

[solar_plasma]

Hi All,

hi

After a year of study and preparation, I started refining a few months ago. So far, I've accumulated 10 gr of gold from computer parts, gold-plated metalware, and gold-filled jewelry. I've had success using two different Aqua Regia (AR) methods, as described elsewhere on this forum:

method #1: boil the pregnant AR down to nearly a crystal, reconstitute with HCl, repeat several times. This eliminates the nitric, and when adding the Sodium Metabisulfite (SMB) the precipitation is immediate and dramatic. On one of my batches, the entire solution turned brown in half a second.

method #2: mix hot water with Urea until dissolved, and then add to pregnant AR until fizzing stops. The fizzing is not noticeable. I have to hold it up to the bright sky to see the tiny bubbles. After an hour or so, it stops. Then I drop the gold using SMB. It takes a long time - 24 hours minimum.

I have three questions for the more experienced members of this forum.

Why the more experienced members?

question #1: which method is superior? The AR boil-down method is slower, but the gold drops faster and is easier to deal with. It's fairly course and filters easily. The AR Urea method is faster, but the gold drops really slowly, and is hard to deal with. The gold is extremely fine, sticks to the sides of the jar, and much of it passes right through my filters. I feel like I'm losing gold using the AR Urea method.

Easy. Both are wrong,if you boiled the first one. Don't boil pregnant solution to get rid of nitric, just evaporate. There is written much about that on the forum. Don't use urea, to get rid of nitric, it could blow your vessel. Avoid any excess of nitric. Use up excess nitric with a gold button or with sulfamic acid, if you could not avoid the excess or use your method 1, but don't boil.

Superior method is not to have excess nitric.

question #2: are there any filters that can filter out the extremely fine gold that precipitates after the AR Urea method? I've tried coffee filters and 11-micron LabNerd filters. It catches a lot of the gold, but not all. I'd estimate 20% is fine enough to pass straight through the filter. And the filter ends up impregnated with the gold as well, and doesn't completely rinse out.

I would decant instead of filter.

question #3: I am having problems with gold adhesion on glass. I have to scrub my glassware with a small brush to get the gold off. What a pain. What is causing this? The glassware was thoroughly cleaned prior to use. I only use distilled water.

You can read this on the first 50 pages of Hoke and Harold also wrote about it: The glassware has to be extremely clean. Don't even touch the inner side. Then you will not have that problem.

 

[Harold_V]

After a year of study and preparation, I started refining a few months ago. <snip>
method #1: boil the pregnant AR down to nearly a crystal,

If you'd like to get and stay on my bad side, just post something like this again. You and I will not get along, and I'll see to it.

If you've been studying for a year, one of the things you should have learned by now is to NEVER mention boiling when you mean to imply evaporation. I've spent way too much of my time trying to have readers understand that's not acceptable, and guys like you are making the job one that never ends. One does NOT boil when evaporating. If you don't understand that, you need to get back to Hoke's book.

WHEN YOU SPEAK OF EVAPORATING, THAT'S EXACTLY WHAT YOU SHOULD SAY. I WILL RIDE YOU UNMERCIFULLY IF YOU MENTION BOIL.

question #3: I am having problems with gold adhesion on glass. I have to scrub my glassware with a small brush to get the gold off. What a pain. What is causing this? The glassware was thoroughly cleaned prior to use. I only use distilled water.

The most likely source of your problem is abused glassware. If your beakers are perfectly clean and in pristine condition, gold won't stick, even if it tends to deposit. From this you should learn that you should use new vessels for precipitation, and that there is no valid reason to precipitate in anything but the vessel in which you will wash the resulting gold. Use a new beaker, and use it ONLY for precipitation. If, in the process of being used, it starts attracting gold that is difficult to remove, demote the beaker to general use, and don't use it for precipitation.

Do NOT wash your glassware with any abrasive compounds, aside from using Bon Ami. It will remove stubborn stains without damaging the surface finish. I used it with total satisfaction for all of the many years I refined. I was the sole person to clean my glassware, by the way, so I know of what I speak.

Read Hoke's book. Read it again. Read it until you understand what she teaches.

Harold