# Hastening the dropping.



## GregerG (Nov 21, 2011)

Sometimes it take a _long_ time for all the gold drop (tested with stannous chloride),
is there something to add to accelerate the dropping/clearing of the solution?

//Greg.


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## Geo (Nov 22, 2011)

chilling your solution will help a little but you should really let the solution settle for at least 24 hours anyway. test the solution after this period to be sure you precipitated all the gold.


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## qst42know (Nov 22, 2011)

At the risk of adding some confusion to your issue. 

If you have added SMB and your solution tests barren for dissolved gold. A brief gentle boil will gather fine particles in suspension and clear your solution quickly.


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## GregerG (Nov 22, 2011)

Thanks! Will try that! 
I know that after the first rinse in hot water the powder settles quickly so I'm sure you are correct...


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## butcher (Nov 22, 2011)

Using too much acid to dissolve gold is a very common mistake, and may be one of the reasons for your troubles.
Also these acids can be expensive and hard to get so using only amount needed just makes common sense.

All of info below is approximated from what C.M. Hoke teaches:

This is based on HCl: HNO3 ratio 4:1,
32% HCl and 70% HNO3,
4 fluid Oz of HCl and 1 fluid Oz will dissolve about one troy ounce of gold,
So: about 119ml HCl and 29.5ml to dissolve a troy Oz gold,
This is about 1/2 cup HCl--1/8 cupHNO3 per troy ounce gold

From above we get:
3.8ml HCl-0.95ml HNO3 to dissolve one gram of gold,
This is about 1/4 tablespoon HCl and less than 1/4 teaspoon HNO3 to dissolve a gram of gold.

For more:
To dissolve 5 grams of gold: 19ml HNO3 and 4.75ml HNO3.
To dissolve 15 grams of gold: 57ml HCl and 14ml HNO3.
To dissolve 25 grams of gold: 95ml HCl and 23.5ml HNO3.

It is best to add the nitric acid in very small increments, using heat to complete reaction between additions, using only amount needed to dissolve the gold, so there will not be much trouble with evaporating off the excess nitric acid later

Even if you use the HCl/ bleach to dissolve gold use of too much acid and oxidizer can be more troublesome.


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## GregerG (Nov 28, 2011)

Thank you for that thoroughal explanation.

I basically use 1ml nitric acid (70%) per gram gold, and 4 times that amount of HCl (30-35%).
But I've always just mixed the acids and then added the gold, and when it's dissolved I've dropped a gold button until it will not dissolve any more.

I'm in the middle of building a fume hood and exhaust so I can use a heating plate in the process too,
so I'll do it your way when its completed 

Thanks again!


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## goldsilverpro (Nov 28, 2011)

GregerG said:


> Thank you for that thoroughal explanation.
> 
> I basically use 1ml nitric acid (70%) per gram gold, and 4 times that amount of HCl (30-35%).
> But I've always just mixed the acids and then added the gold, and when it's dissolved I've dropped a gold button until it will not dissolve any more.
> ...


If you cover the gold with a little excess HCl (about 150ml/oz of gold or gold alloy), heat it 'til you see a little steam, and feed the nitric in increments 'til there is no more reaction, you won't have to put a gold button in. Adding the acids individually is actually better than pre-mixing because you have much more control over the dissolving and the fume production.


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## butcher (Nov 29, 2011)

GregerG,

From reading a post you made in another place, it seems to me you may have tried using aqua regia on gold with much base metals, is this what you have?

How about telling us what you did with what, telling us all details, not leaving out the tiny detail even if you think it is unimportant, that way we may be able to help, I have a feeling you’ve got a mess on your hands.

But be ready to hear how you have a mess and need to read Hokes book.

Post in one thread (your trouble), that way you will get a better answer not partial answers form several members not seeing your whole question or problem.

My guess is you have many mistakes compounded on top of each other, most all of us have made these mistakes when we first started.


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## GregerG (Dec 4, 2011)

I have all kind of mixtures, pure gold, gold and copper plating (every other layer), and gold + tungsten every other layer,

And I think I got this down processspretty good, gold button is barely even touched, and trying with urea it stops fizzing really fast.

Now for the original question - it was just a matter of _me_ being to impatient. 
Heating it worked like a carm, the dust settled at once!


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## goldenchild (Dec 4, 2011)

qst42know said:


> At the risk of adding some confusion to your issue.
> 
> If you have added SMB and your solution tests barren for dissolved gold. A brief gentle boil will gather fine particles in suspension and clear your solution quickly.



I second this. It not only helps the gold settle much faster but will also clump the gold together making for easier decanting.


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## kadriver (Dec 5, 2011)

goldenchild said:


> qst42know said:
> 
> 
> > At the risk of adding some confusion to your issue.
> ...



I have been plagued with waiting, sometimes for hours, for the suspended gold to settle before getting rid of the liquid.

I have even resorted to filtering out the suspended gold as I was pressed for time. Sometimes part of the gold powder would go through the filter paper and I would have to filter it a second time through the same filter paper until all the gold was trapped in the filter paper and the solution ran clear.

I would then put the filter paper in a melt dish set aside specifically for this purpose. Cover the filter paper with borax and using a low flame, burn the gold laden filter paper while adding more borax to keep the ashes from departing the melt dish. A small gold bead would appear in the molten borax. I would pluck it out and add it to the next batch of gold that I refined.

I just happened across this post and see a very simple solution to this settling problem that I have had for over a year now.

If I can avoid all that process above by just heating to a gentle boil, then... well it just sounds too good to be true.

Let me make sure I have the process straight; After dropping the gold with sodium metabisulfite, all I need to do to get the rest of the gold that is suspended to join the gold powder in the bottom of the container is give it a gentle boil?

I say it again, it seems too easy to be true, but I will surely try it with my next batch of karat scrap that I refine.

I learn something of value each time I visit this forum.

kadriver


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## qst42know (Dec 5, 2011)

I believe I first heard of this elegant solution from Lou several years ago for another solution that refused to filter. 

I expect you will find it much less trouble than you have been going through. You can decant in about a 1/2 hour or so. It will clear a dirty gold solution it just won't clump as tightly.


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## butcher (Dec 5, 2011)

A little off topic but related,

Heat can accelerate a chemical reaction, mix chemicals, or help with contact in solutions, it can also make salts in solutions more soluble, a useful tool in your lab, chilling also a very useful tool, can make salts form faster, make most things less soluble.
These tools keep them in mind, in your toolbox, and in your processes, learn how to use them to your advantage.

Here is a simple example:
Say I have a pot of silver chloride, lead chloride, and gold, and I need to clean it up.
Heat and water will be my choice, silver and lead chlorides are insoluble powders
(In water) powders with my gold, but heating the water will make the lead chloride much more soluble, so I may bring pot to boil, lower heat to just under boil, let silver settle in this very hot solution (put lid on go walk away for hour or so), then decant (with suction tool), the soluble lead chloride solution (into canning jar#1), add more water to pot and boil again (lead in canning jar#1 sits in very cold outside or fridge in summer to chill out the lead as insoluble salts), now lower boil on pot to under boil to let gold and silver powders settle (cover and walk away for a while), decant hot water solution of lead chloride into jar #2, take jar #1 (decant water from lead salt)take this cold water and put back into boiling pot to collect more lead, (chill out lead from jar #2) and so on,
This can also be done just using one jar.

Another example:
Say I have a powder or metal to dissolve, and I want to save on the solvent solution being used (acid or what ever solvent), the metal powder (salts) are more soluble in hot solutions than cold solutions, or the metals dissolve in the acids (more salts held in hot acid than cold acid), well I can use a principle similar to the one in the example above, heating the solvent dissolves more (metals into solution or salts of metals) decanting hot saturated solution to another cooling jar, letting this jar cool will precipitate out a portion of its metals salts (and usually the more valuable ones first, but also can be a mixture), and now the solution at a lower temperature in jar (holds less metals ), can be returned to the heating pot temperature raised and it will collect more metals at this higher temperature, repeating this over and over you can remove one metal from another using the same solution with less waste generated.

Crystallization and re-crystallization to make metal salts pure, are also related to this subject, and this idea can be used when your making your purifying your metal salts with crystallization methods

Edited to add this thought: 
You can also use this idea with gold in a solution, a hot solution will saturate with gold salts, a cold solution will hold these less of these gold salts, heat and chilling can be used in similar fashion as noted above to get cleaner gold powders in decanting jar (remembering a portion of gold is held in solution) (remembering most base metals stay in solution easier than gold, (also consider reactivity series of metals), 
Think re-crystallization of gold salts.
Hard to explain hope you get the idea.


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## TBarrow (Dec 5, 2011)

Butcher,

Nice helpful post, thanks. Good examples.

Todd


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## goldenchild (Dec 6, 2011)

kadriver said:


> goldenchild said:
> 
> 
> > qst42know said:
> ...



I used this technique several times yesterday night as I am running several batches at once and can say its definitely valid. You simply drop the gold and place your beaker on a hot plate. It can be done immediatly after the drop. No need for waiting. I actually bring mine to a rolling or near rolling boil and have the gold settled in five to 10 minutes. Depends on how much liquid is in the beaker. In my experience the result has always been clumpier gold that is easier to decant. This is a rare case of very good and true.


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