Why won't my gold precipitate?

shop deals on amazon
Advertise with us
xelexo
Shop deals on ebay
Gold Refining Forum

Help Support Gold Refining Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Airman8403

Airman8403

Member
Joined
Jun 10, 2010
Messages
7
I had approximately 8 ounces of Auric Chloride that I wanted to drop gold out of yesterday using Sodium Metabisulfite. Following the directions for mixing that came with my SMB, I mixed 0.5 dry ounces of SMB with 4 ounces of boiling distilled water. After this solution was clear, I added it to my 8 ounces of AC and stirred it thoroughly. I didn't notice any immediate response aside from a strong stinging fume so I put it up to work overnight. This morning when I went to check on my mix, I had only the slightest dusting of precipitate on the bottom of my jar and the liquid still had a yellow tint. Testing the liquid with stannous chloride, I got an immediate dark brown response. Referring back to LazerSteve's videos, I noticed that he mentioned diluting his AC 3 times over (which I took to mean 3 parts water to 1 part AC) which I failed to do before adding SMB. I decided to give this a try and added 24 ounces of distilled water to my 8 ounces of AC and 4 ounces of SMB solution. After about an hour, I still see no further reaction aside from a lighter solution and now when testing with stannous chloride, I'm getting a weaker response. I know my gold is still in there, I just don't know what I'm doing wrong in getting it to precipitate out. Any advice would be appreciated. Thanks. - Bryan D.
 
There are a few things we need to know before we can help you. First of all can you provide a pic of what you have now.
2. where did the Auric Chloride come from?
3. how much gold was dissolved to make the auric chloride?
4. did you make sure the Auric Chloride was free of nitric acid?
 
In addition to what Goldenchild has asked, a brown reaction sounds like a false positive in the presence of iron.

An acidic solution that is saturated with SO2 (from SMB) and reacted with a high reactivity base metal (tin in the stannous) will produce hydrogen sulfide gas and/ or sodium sulfide. These precipitate dark brown, gray, or black precipitates with many base metals . A tell tale sign of the false positive is a faint smell of rotten eggs on the test swab. This gas is very deadly so don't go huffing a cloud of it, just a faint hand waft over the swab will do.

To confirm gold when a false positive is suspected use ferrous sulfate (copperas) to test for gold. Copperas produces a dark brown to black colored precipitate of elemental gold, the same color as your gold powder. Perform this test in a small test tube or on a spot plate.

I would bet you got all the gold, but I could be wrong, you may have too much oxidizer in the solution. This is evident when the test swab stain vanishes after a short time.

Steve
 
Diluted Auric Chloride.JPGStannous Chloride.JPG

Here is a picture of the solution I still have as well as a picture of my stannous chloride test result.
 
Where did the Auric Chloride come from? The AC was made from foils I stripped from memory sticks as well as the precipitate I accumulated from a recent batch of aqua regia.

How much gold was dissolved to make the auric chloride?
I couldn't say with any accuracy unfortunately. This was my first attempt at refining and I'm afraid I've got a bit to learn about record keeping.

Did you make sure the Auric Chloride was free of nitric acid?
I can't think of anywhere my AC would have picked up any nitric acid outside of the precipitate from the AR but I rinsed that repeatedly with tap water AFTER it was treated heavily with urea and SMB.

Let me know if there is any other info I could provide. Thanks again. - Bryan D.
 
That's the real question. It takes maybe a half a pound of fingers
to yield one gram of gold. There's not a lot to see on the bottom of
your beaker if you didn't start with many fingers or AR residue.
 
The same thing just happened to me! I processed over 600 grams of fingers with AP and then disolved with clorox. When I added the SMB I got an immediate clearing of the solution, now a day later still clear!! I guess I got a bad batch of SMB from an Ebay dealer!
 
jpullen said:
The same thing just happened to me! I processed over 600 grams of fingers with AP and then disolved with clorox. When I added the SMB I got an immediate clearing of the solution, now a day later still clear!! I guess I got a bad batch of SMB from an Ebay dealer!
Click to expand...
Did you make sure that all the chlorine was removed from the solution, by heated evaporation or letting it sit in the sun (I haven't seen one of those for 4 days!) ? An excess of chlorine will keep gold dissolved in solution.
 
That could be the problem! The cold weather may have slowed the evaporation of chlorine. After allowing more time for evaporation, should I add more SMB?
 
Someone with more experience will be able to give you a more definite answer, but from my limited experience, & as I tend to add too much SMB, letting a solution set for a few days has at times produced results. Since you are starting (wisely) with a smaller drop, some of the gold may be extemely fine (colloidal) & may need extra time to drop.
Have you been able to make & use some stannous chloride for testing yet? you can use 95/5 solder (95% tin, 5% silver) a 2" piece dissolved in a few tablespoons of Muriatic/HCl, heated until the wire starts to bubble. This would tell you that you still have gold in solution, as well as the relative concentration.
Depending on the quality of the fingers you started with, you should expect from 2-3 (low to high) grams of gold from 600 grams of fingers, i believe.
good luck!
 
Thanks dtectr, I'm just in the play stage now, after having read alot of material and posts on this forum, I'm starting to experiment a little. Any advice is helpful.
 
jpullen said:
Thanks dtectr, I'm just in the play stage now, after having read alot of material and posts on this forum, I'm starting to experiment a little. Any advice is helpful.
Click to expand...
Play with a purpose is called "learning". It all depends on the teacher. Look at Hoke's familiarization experiments as an example of that.
Keep good notes for yourself & follow safety guidelines while you do so. Then you'll understand the "why's" when you do the "how's".
good luck & keep us posted with your progress.
 
joem said:
would a couple of drops of fish tank chlorine eliminator do the trick?
Click to expand...

Can't see any good in that...


jpullen said:
The same thing just happened to me! I processed over 600 grams of fingers with AP and then disolved with clorox. When I added the SMB I got an immediate clearing of the solution, now a day later still clear!! I guess I got a bad batch of SMB from an Ebay dealer!
Click to expand...

Did you test you solution?
If positive, you can add just a little more SMB and let it stand on hot plate with low heat for hour or two, warm solutiont precipitate quicker.

tell us what is happning when adding the SMB (fizzing, brown gas etc'...)

on a side note, i find it hard to believe that 1-2 gram of gold in solution do not react at all and do not show even the slightest precipitation action, are you sure you didn't dissolved any (most of) gold with your AP process ?
 
I tested the solution and got a positive. Warmed as suggested and it dropped! No doubt that the chlorine had not evaporated; we had really cold temps here in N. Florida last night, although it was not outside; It was in the garage!!
 
Airman8403 said:
Here is a picture of the solution I still have as well as a picture of my stannous chloride test result.
Click to expand...
Pictures not included in this response, but both of the pictures are in keeping with what you have---almost no gold in solution, and a hint of a brown reaction that is common when a solution borders on being barren. Gold can be tested to the point where it's not worth recovering---that's how sensitive the test is with stannous chloride.

One thing that will really help you guys is knowing that if you have gold in solution in acid, it will always have color. That's not true of gold dissolved with cyanide, but that's not the point at hand. So then, when you introduce the precipitant of choice, especially if there's precious little value in solution, you can expect the solution to shift towards no color. That's exactly what it's supposed to do (assuming you don't have base metals present).

When you have a clear solution, chances that there's anything of value included is zero. However, that a solution has a given color may or may not indicate the presence of values. Bottom line is you test---you test with stannous chloride, ferrous sulfate, DMG and anything else you can use to make determinations of why a solution has color. After you've done this for a while, it becomes routine and you can predict what you're seeing.

It's a little frustrating working with tiny amounts of gold, for the reactions may not be as pronounced, but it can save you a lot of grief if you screw up. While gold isn't lost unless you discard a solution, there may be times in the learning curve where you'd better off to discard a solution where you've really screwed up instead of trying to salvage what is a bad deal. If the amount of gold that is present is small, there's not much of a loss.

Having said the above, remember---when all else fails, you can send troublesome solutions to the stock pot. There you will recover the values-----but it recovers everything from copper and beyond.

Harold
 
jpullen said:
I tested the solution and got a positive. Warmed as suggested and it dropped! No doubt that the chlorine had not evaporated; we had really cold temps here in N. Florida last night, although it was not outside; It was in the garage!!
Click to expand...

I'm glad it worked out well, now we are waiting for your post in the gallery section :mrgreen:
One most always consider the temperature of solutions, it has a dramatic effect on reactions.
 
Just wanted to say the last 2 small drops I did got harder and harder to drop.
I will try heating the solution now, the weather here got colder and I can see the effect it has on dropping the gold.
It appears the chlorine can't dissapate very quick at all.
 

Latest posts

Back
Top