# Orange / Red Auric Chloride



## gold4mike (Oct 14, 2011)

I'm processing the result of another person's failed attempt at recovery from e-waste. I received the buckets of AR with pieces of ceramic processors and board remnants such as aluminum capacitor bodies still in the bottom.

I've filtered off the liquids, cemented with copper and started refining the cemented PM's. On my second refining of some of the solids I got an Orange/Red color instead of the Yellow I was expecting.

I've dissolved the gold powder in HCl/chlorine and the color went to Orange/Red almost immediately. I have seen this similar color when I have a concentrated solution of Auric Chloride but this color appeared immediately upon dissolution.

The gold powder in question had been dropped from the AR using Sodium Metabisulfite, followed by three HCL washes and three water washes. I didn't use an ammonia wash, but probably will once I drop it from this current dissolution.

Am I just overthinking this or do I possibly have something else in with the gold that I need to deal with?


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## Anonymous (Oct 14, 2011)

Possibly palladium.


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## gold4mike (Oct 14, 2011)

How would you suggest I proceed from here?


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## goldenchild (Oct 14, 2011)

Simply drop your gold and test the remaining solution. If there is Pt/Pd in solution ppt the Pt and then the Pd.


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## samuel-a (Oct 14, 2011)

Those are kinda odd results Mike...

If you actually do have some PGM's contaminates (and it is a reasonable suggestion), it may be a little hard to detect with SnCl2.


If you ever tried to dissolve pure Pd (or nearly pure), you should know that only few mg of dissolved metal in 1 liter will give a rich brown/red solution.
As you probably know, DMG will quantitatively drop all Pd from solution.

SMB, i known to drag other metals with it, especially Cu (I) and Pd.
Where no DMG is available, you may consider dropping the gold with oxalic acid and test the remaining solution for PGM's more easly.


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## Harold_V (Oct 15, 2011)

samuel-a said:


> Those are kinda odd results Mike...
> 
> If you actually do have some PGM's contaminates (and it is a reasonable suggestion), it may be a little hard to detect with SnCl2.


This is an excellent example of why one should understand testing. 

In a case such as this, I'd place a drop of the chloride solution in a spot plate cavity. I'd then add a crystal of ferrous sulfate, to precipitate gold. If the crystal is large enough, it will precipitate all of the gold, allowing a stannous chloride test to define what else may be present. If, upon the removal of the gold, the solution shifts so it's clear of color, most likely there is nothing present. 

You can expect very little in the way of palladium if the solution is orange. It takes on a dark brown color rapidly if there's much present. If this is a second dissolution, it's highly unlikely there will be much, however, unless the previous batch was recovered by cementation instead of selective precipitation. 

Harold


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## gold4mike (Oct 17, 2011)

The initial batch WAS obtained by cementing on copper.

I cleaned the powder using HCl rinses and water rinses and did this second dissolution. 

The solution has now been sitting for more than a week since I'm busy with other projects. I looked at the solution yesterday and it has lost the red/orange color. It now looks like my usual Auric Chloride.

I'll follow Harold's suggestion and test with Ferrous Sulphate. I have grown confident in my ability to read the results of Stannous Chloride tests and I always drop with Sodium Metabisulphite. I'll get some Ferrous Sulphate and do some more learning.

Thank you everyone for your suggestions. My quest for knowledge continues!


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## Harold_V (Oct 18, 2011)

Don't forget the value of testing with DMG where palladium is concerned. There are times when a solution has a sparse showing of gold, and can be confused with a palladium reaction, or even one of platinum. That's most likely when the stannous chloride solution is bordering on being useless, however, but it's information that can help. Mean time, a solution thought to contain palladium, even traces, is best tested with DMG, which is VERY sensitive. The canary yellow response is hard to misinterpret. 

Harold


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## Alentia (Feb 28, 2012)

This is interesting...

I think I got the same problem. I am doing purification of gold powder dropped first time with SMB (SO2) and now with Oxalic. While I have dropped 64% of gold the rest won't drop. My solution is bright yellow/red color and no matter how much oxalic I add gold won't precipitate. For 103 gram of gold (after first precipitation with SMB) I have used 125(initial)+10+15+10 gram of Oxalic. Last 10 gram resulted in no precipitation. Solution was boiling and stayed clear orange color. Stannous shows strong presence of gold and Pt/Pd group. On the picture the test of the left was done after oxalic stopped dropping more gold, on the right when I have reduced diluted solution to half by boiling/evaporation.

I can probably introduce some SO2 using SMB, but it will not serve the purpose of re-refining, as I will be dragging all Pt group back down to powder.

Should I try to drop Pt first using Ammonium Chloride?
What happened with the excess (10 grams) of Oxalic?

It looks like my solution is too acidic and I need lower the PH, that might be a good reason why gold is not dropping.


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## garage chemist (Feb 28, 2012)

I know about this incomplete gold precipitation with oxalic acid. It has happened to me every time I re-refined gold.
You have to slowly neutralize the boling hot Au(III) + oxalic acid solution with NaOH or Na2CO3. As the pH approaches less acidic values (the chloride from the HAuCl4 solution is converted to HCl, remember that!), the gold will be quantitatively reduced and precipitated. Don't make it completely neutral or alkaline though, or the contaminating metals could precipitate too! Use a round-bottom flask with vertical Liebig reflux condenser for this, the fizzing from CO2 evolution otherwise leads to serious loss of values. 
The neccesity to neutralize the gold reduction with oxalic acid is mentioned in Brauer's third volume, the one that deals with gold and the PGMs, and which was a valuable guide for me during my dental gold refining adventures. Brauer recommends to neutralize with ammonia, but I can't recommend this since there is the danger of precipitating fulminating gold if too much is added (happened to me once- canary yellow, fine powdery precipitate) which can blow up your whole batch if it explodes. No such danger exists with NaOH or Na2CO3.
It is a mystery to me why Hoke fails to adress the incomplete oxalic reduction when failing to neutralize. I think that she simply didn't know. 

Even better that neutralizing the oxalic reduction would be to use disodium oxalate for the reduction instead of oxalic acid. No danger of too high pH exists when using this. If the solution is too acidic and the reduction incomplete, simply add more disodium oxalate.


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## dtectr (Feb 28, 2012)

Both solutions are very hot, correct? 
Hoke


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## lazersteve (Feb 28, 2012)

I've never heard of the incomplete reduction when using oxalic acid, but apparently it can be a real problem.

I've always used potassium or sodium oxalate for gold reductions as discussed here for BDG:

Alternate Oxalate Precipitations Discussion

and

Alternate Oxalate Formulas

Reading that old thread makes me want to get back to using my dibutyl carbitol again.

Steve


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## Alentia (Feb 28, 2012)

dtectr said:


> Both solutions are very hot, correct?
> Hoke



Both solutions are boiling hot.


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## Alentia (Feb 29, 2012)

Just came back...

Ran 2 test solutions before proceeding to big flask.

1. Big flask with 2.5L of solution with about 36-38 gr of gold
2. Took 250 ml out of flask to 2 1L test beakers 125ml each
a. Beaker 1 kept adding Na2CO3 at 12 grams solution would still show acidic at about 3-4 PH
b. Added 3 gram of Oxalic and all of the sudden PH went to 7, everything dropped which looks like gold dust after first treatment with HNO3. Not nice.
As solution has Pt/Pb group everything got mixed. Will have to re-refine
c. Beaker 2 added 5ml of ammonia, fizzling but nothing
d. Beaker 2 added 3 gr of diluted Oxalic, no effect
e. Added 10.5 gr of Na2CO3 and reaction started. Beaker 2 dropped nice chunk for 1.6gr
f. Tested remaining solution with stannous, resulted in orange color, added Ammomium Chloride - pink powder precipitated, left overnight. Still can see some gold flakes flowing in the water though.

Now to the big flask:
3. Added 168ml of Na2CO3 diluted with 5 parts of water to big flask
4. Added 40 gram of Oxalic - reaction started, but it seems some gold was dissolving again
5. Added another 5 gr of Na2CO3 and left overnight. Reaction was going chunks was forming and dropping. PH was still sitting around 3-4


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## Alentia (Mar 4, 2012)

Interesting development from "Beaker #1" from above:

1. Washed and heated precipitates in water
2. After about 15 min into boiling all precipitates dissolved into Choloroauric Acid
3. Added filtered precipitates from filter
4. Precipitates dissolved into yellow liquid
5. Dropped gold with SMB
6. Melted - nice color without any shades, tested for 24K

Notice: precipitates were unusual, the 30% of particles were passing through medium filter.


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## etack (Mar 6, 2012)

I'm not sure you really want to boil your solutions you will evaporate your values.

I once boiled away ten grams. I know I did because I found a pretty gold sheen over an other solution that I had already precipitated and removed the gold from. It was pretty, and pretty sad. No more boiling after that.

Eric


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