# Why won't my gold precipitate?



## Airman8403 (Jun 25, 2010)

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.


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## goldenchild (Jun 25, 2010)

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?


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## lazersteve (Jun 25, 2010)

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


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## Airman8403 (Jun 25, 2010)

Here is a picture of the solution I still have as well as a picture of my stannous chloride test result.


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## Airman8403 (Jun 25, 2010)

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.


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## lazersteve (Jun 25, 2010)

How many memory sticks and how much residue from the first AR batch?

Steve


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## glorycloud (Jun 25, 2010)

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.


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## goldenchild (Jun 25, 2010)

By the looks of that crystal clear solution it looks like you go all the gold out.


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## jpullen (Dec 14, 2010)

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!


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## dtectr (Dec 14, 2010)

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!


 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.


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## jpullen (Dec 14, 2010)

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?


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## dtectr (Dec 14, 2010)

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!


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## jpullen (Dec 14, 2010)

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.


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## dtectr (Dec 14, 2010)

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.


 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.


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## joem (Dec 14, 2010)

would a couple of drops of fish tank chlorine eliminator do the trick?


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## samuel-a (Dec 14, 2010)

joem said:


> would a couple of drops of fish tank chlorine eliminator do the trick?



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!



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 ?


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## jpullen (Dec 14, 2010)

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!!


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## Harold_V (Dec 15, 2010)

Airman8403 said:


> Here is a picture of the solution I still have as well as a picture of my stannous chloride test result.


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


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## samuel-a (Dec 15, 2010)

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!!



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.


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## adam_mizer (Dec 20, 2010)

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.


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## Oz (Dec 20, 2010)

I am not a chemist so I can not give you an exacting solubility curve but the solubility of Cl2 gas (chlorine gas) is increased with lower temperatures and decreased with higher temperatures. This is why heating your solution drives out the free chlorine.

It may also be of interest to you that the solubility of the SO2 that is generated from your SMB will behave the same way as to how much of the gas is able to be held within your chloride solution at a given temperature. This is why Harold used to ice his highly concentrated solutions of auric chloride in order to counteract the heat that was generated from the reaction. 

Cold temperatures can be your friend for some reactions.


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## lazersteve (Dec 20, 2010)

adam_mizer said:


> 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 dissipate very quick at all.



The speed at which the chlorine dissipates is temperature dependent. Other factors would be the volume of water in the solution and if there is still a chlorine producing reaction going on in the solution. If the reaction keeps producing chlorine at a rate greater than it is dissipated, then the chlorine levels would no decrease.

Working with HCl-Cl is like working with nitric acid in the sense that if you use excessive amounts of oxidizers (nitric= NOx or bleach=Cl) to get a fast dissolution, you end up with the problem of removing them to get the gold to precipitate. Matter can not be created or destroyed, it merely changes forms. For this reason if you add too much of a reagent to your reaction during the dissolution stage, it will have to be removed before precipitation can occur.

Steve


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## adam_mizer (Dec 20, 2010)

The heat/warmer drove the chlorine out pretty much right away. Several minutes of low/warmer.
Well I've been eyeballing this pretty good lately.
Decide on a measured amount of HCl, on a small amout its just a hair too much maybe, been trying less and less. 
Then drop in a tiny amount of clorox, and again just until a reaction is working which amounts to about 25% or less of the HCl poured in. 
Just to use barely enough to take all the gold into solution over a few minutes time.
My ambient temp may be 40 or below, and above 45 worked better. There's a difference.

Now I havn't seen the other end of this spectrum when its actually too hot of an ambient temperature.


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## lazersteve (Dec 20, 2010)

You'll also find that actively stirring the mix will promote a faster dissolution of your gold and also produce the maximum amount of chlorine from each Clorox addition.

Steve


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## dtectr (Dec 20, 2010)

Do I have this right??

Not to get side-tracked - i believe this is relevant ...

According to info re: Plattner's Process:
"Chlorine gas will react with gold. 

Typically the reaction is done at elevated temperatures or in the presence of aqueous HCl at lower temperature." [from lazersteve] http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=5815&p=50167&hilit=plattner#p50167 
Using a minimum of HCl minimizes the dissolution of base metals (acc. to Ammen). Using HCl:Clorox at a ratio of 1:1.5 in a sealed vessel, rolled to effect maximum exposure of Gold to chlorine gas. 
At lower temps only as much HCl to initiate the reaction & time to allow chlorine gas to develop, accumulate, & dissolve gold. So extra Clorox is better than extra HCl, as long as it is expelled sufficiently before precipitation is attempted.

Is this a correct interpretation??

any feedback appreciated.
thanks


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## lazersteve (Dec 20, 2010)

My observations using HCl and Clorox is that it works better in the cold and faster with more diluted HCl. This also requires less zinc to precipitate PGMs when processing cats. 

The quote you posted of mine concerning chlorine at high temperatures is a reference to gas phase extractions, not aqueous ones.

I would not read too much into the quotes you have posted. It seems as though you are headed in the direction of selective extraction of gold using HCl-Cl and I can tell you from experience with this idea, it has hidden problems. The biggest problem with attempting to use HCl-Cl selectively for gold is the fact that the other base metals work against you by cementing your gold out of the solution.

Steve


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## dtectr (Dec 21, 2010)

that's what i was wondering - butcher always adds the comment, regardless of process, e-scrap or ore, that if base metals are still present, they WILL cement out some values & if the ratio is high enough, the process may slow or stop altogether.

what about the amounts of Clorox added? I know the more I add the more I have to worry about dissipating, but that aside - is having too much chlorine an issue, as to effective dissolution of gold?

I'm sure this has been covered elsewhere - problem-solving as in this post help me to see these procedures in real-life scenarios, which, because of my ADD, is how I learn & retain. You can imagine which of my instructors in school thought I wa a genius/moron ! :lol: 
thanks again


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## lazersteve (Dec 21, 2010)

Once the solution is saturated with chlorine, which depends on the temperature of the solution and it's acidity, any additional chlorine produced goes up in smoke as a greenish-yellow chlorine vapor. If you are seeing chlorine vapors rise out of your solution, it is saturated and you are wasting Clorox by adding more.

At this point you need to stir and apply low-medium heat until all of the chlorine reacts with the gold or is driven out by the heat.

Once the chlorine is either used up or driven out of solution, either add more Clorox ( if there is still undissolved gold) with stirring or stop the reaction and allow to cool, then filter, if the gold is all dissolved.

Steve


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## dtectr (Dec 21, 2010)

thats exactly what i was wondering - thanks.


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