how to refine silver chloride out aqua regia

[tj1466]

hi my name is tony and i am new at this job i need some help whit refining silver chloride out aqua Regia what is a good way thank you 8)

Tony:
Please do NOT post the same question more than one time on the forum. Regardless of where it is posted, it will be read by those of us that are willing to help.

Take note that I have deleted your other post, a duplicate of this one.

Harold

 

[geonorts]

filter

 

[butcher]

Very little silver will be in aqua regia as AgCl2, as silver is insoluble as a chloride and silver chloride is also insoluble in acids, some AgCl does get oxidized by the strong acidic Aqua regia to form AgCl2, which is a contaminate for our gold solutions. By adding water diluting the acid will convert it from AgCl2 to AgCl silver chloride a white fluffy powder (note lead chloride also an insoluble chloride,and will look very similar white powder) let this sit overnight for silver chloride to settle, decant and filter solution, silver chloride powder rinsed saved for later removal of lead (boiling hot water) and conversion to silver metal before melting, lye caustic karo syrup method or iron and sulfuric method or aluminum hydrochloric method, you can read up about these on the forum.

 

[tj1466]

Very little silver will be in aqua regia as AgCl2, as silver is insoluble as a chloride and silver chloride is also insoluble in acids, some AgCl does get oxidized by the strong acidic Aqua regia to form AgCl2, which is a contaminate for our gold solutions. By adding water diluting the acid will convert it from AgCl2 to AgCl silver chloride a white fluffy powder (note lead chloride also an insoluble chloride,and will look very similar white powder) let this sit overnight for silver chloride to settle, decant and filter solution, silver chloride powder rinsed saved for later removal of lead (boiling hot water) and conversion to silver metal before melting, lye caustic karo syrup method or iron and sulfuric method or aluminum hydrochloric method, you can read up about these on the forum.

thank you

 

[saadat68]

Very little silver will be in aqua regia as AgCl2, as silver is insoluble as a chloride and silver chloride is also insoluble in acids, some AgCl does get oxidized by the strong acidic Aqua regia to form AgCl2, which is a contaminate for our gold solutions. By adding water diluting the acid will convert it from AgCl2 to AgCl silver chloride a white fluffy powder (note lead chloride also an insoluble chloride,and will look very similar white powder) let this sit overnight for silver chloride to settle, decant and filter solution, silver chloride powder rinsed saved for later removal of lead (boiling hot water) and conversion to silver metal before melting, lye caustic karo syrup method or iron and sulfuric method or aluminum hydrochloric method, you can read up about these on the forum.

Hi
If we have zinc, iron, and silver in AR solution, Can we precipitate silver with this process ( Add some water )?

 

[kernels]

As stated above, you don't usually have silver in a AR solution. Solubility of Silver Chloride in water is only: 520 μg/100 g at 50 °C

Diluting a solution that contains a bit of Silver Chloride usually causes the solution to go cloudy as the Silver Chloride precipitates out.

 

[FrugalRefiner]

Dilute it and cool it.

Dave

 

[Geo]

Silver nitrate is a liquid and silver chloride is a solid. Due to silver nitrates affinity to HCl, silver chloride forms as soon as the HCl is introduced to the solution. In an AR solution, the silver can dissolve if there is an excess of nitric acid but it will precipitate out almost immediately as solid silver chloride. Heat plays a part in how much silver the solution can hold as a liquid. The hotter it is, the more silver it can hold. The cooler it is, the less silver it can hold.

 

[g_axelsson]

As stated above, you don't usually have silver in a AR solution. Solubility of Silver Chloride in water is only: 520 μg/100 g at 50 °C

True for pure water, but a lot more complicated for any chloride salt mixture.
http://www.saltlakemetals.com/Solubility_Of_Silver_Chloride.htm

Diluting a solution that contains a bit of Silver Chloride usually causes the solution to go cloudy as the Silver Chloride precipitates out.

This works well in any case. Look at the last table on the website above to see why, the solubility of silver chloride spikes when a saturated chloride solution is used, in AR it is gold chloride or HCl that increases the solubility when it gets close to saturation.

Göran

 

[butcher]

In a high chloride solution (like concentrated aqua regia converted to mostly gold chloride and remaining gases as ions in solution) or a concentrated salt of chloride or other common ions in solution, like NaCl, CuCl, the silver chloride (AgCl) can be oxidized to a higher state (loss of electrons), and form a silver chloride salt in a higher oxidation state called dichloro silver Ag2Cl2.

Silver in this higher oxidation state is not stable, and so by simply diluting the high chloride solution (gold chloride solution or the ionic chloride solution), we can reduce (give back electrons to the ions of silver) reducing the Ag2Cl2 dichloro silver back to the lower oxidation state of being the AgCl silver chloride. Which will precipitate out of solution on standing with time.

There are other metal salts which can become more soluble in a highly concentrated environment of common ions--- called the common ion effect...

 

[g_axelsson]

In a high chloride solution (like concentrated aqua regia converted to mostly gold chloride and remaining gases as ions in solution) or a concentrated salt of chloride or other common ions in solution, like NaCl, CuCl, the silver chloride (AgCl) can be oxidized to a higher state (loss of electrons), and form a silver chloride salt in a higher oxidation state called dichloro silver Ag2Cl2.

Silver in this higher oxidation state is not stable, and so by simply diluting the high chloride solution (gold chloride solution or the ionic chloride solution), we can reduce (give back electrons to the ions of silver) reducing the Ag2Cl2 dichloro silver back to the lower oxidation state of being the AgCl silver chloride. Which will precipitate out of solution on standing with time.

There are other metal salts which can become more soluble in a highly concentrated environment of common ions--- called the common ion effect...

I'm pretty sure it isn't about oxidation and reduction, just creation of silver chloride complex. Silver is still in +1 and chloride in -1.

I tried to find any literature about this but the only thing I found was from chemspider and other similar sources, showing that the formula was Ag₂Cl⁺ + Cl^-.

Göran

 

[anachronism]

Goran

Butcher is correct in what he's saying. When you have ions floating around a concentrated chloride based solution oxidised to a higher state the chemistry of the dropping mechanism alters significantly. The interactions change. The +2 and +3 and +4 ions (dependent upon the relevant base metal)need to be reduced to a lower state in order to allow true precipitation to take place. High valency base metal ions can and do oxidise gold too, so you can add precipitant and end up in the same precipitate/redissolve scenario that you have with excess Nitric in solution.

This cycle does reduce those base metal ions down to their lower levels and once this occurs precipitation happens as per normal. It's one reason why trying to calculate the required amount of SMB to drop gold from a random pregnant AR solution cannot be done stoichiometrically.

 

[Lou]

Goran

Butcher is correct in what he's saying. When you have ions floating around a concentrated chloride based solution oxidised to a higher state the chemistry of the dropping mechanism alters significantly. The interactions change. The +2 and +3 and +4 ions (dependent upon the relevant base metal)need to be reduced to a lower state in order to allow true precipitation to take place. High valency base metal ions can and do oxidise gold too, so you can add precipitant and end up in the same precipitate/redissolve scenario that you have with excess Nitric in solution.

This cycle does reduce those base metal ions down to their lower levels and once this occurs precipitation happens as per normal. It's one reason why trying to calculate the required amount of SMB to drop gold from a random pregnant AR solution cannot be done stoichiometrically.

Just bear in mind that aqueous silver is always monovalent, complexed or not!

Now insofar as stoich goes...use an ORP meter to tell speciation and an ICP to tell concentration. Two very necessary tools for anyone doing this on a serious level.

 

[anachronism]

Thanks Lou, I should have been clearer about the fact I was referring to the base metals. 8)

 

[4metals]

I have found if you keep your total dissolved metal concentration under or around 200 grams per liter there is never a problem. (Actually the working number is 233 grams but I prefer to keep it simple so I say 200. I'm a KISS kind of guy.)

Many times I have been asked about problem solutions while at a refinery and in every case they just kept adding metal until the reaction died. Then there was a thick soup with saturated metal levels (and often cemented values which they have no clue about) which doesn't filter or drop clean metal.

The fix is simple, dilute it, try to stay under 200 grams of dissolved metal per liter. And if silver is on the mix, keep it cool. 8)

 

[anachronism]

I'd not heard of that 200g of metal per litre thing before. That makes a lot of sense especially when I'm used to ramming as much per litre into a solution to keep reagents costs down and waste to a minimum.

 

[4metals]

I'd not heard of that 200g of metal per litre thing before.

That's because it is a number that I have calculated from my karat gold refining days when I started to use closed reactors. Before that, I was taught you mix 3 parts HCl and 1 part HNO₃ in a bucket and shovel the scrap in until it doesn't dissolve anymore. Actually it wasn't even that sophisticated, it was more like up to this line with HCl and up to this line with HNO₃.

It worked in a bucket, but overuse of nitric was rampant. But we are also talking 1970. When I switched to sealed reactors it was more difficult to change out the solution so I wanted to define the capacity for each size vessel. Since mixed karat lots have different concentrations of base metal, there was some variation. I settled on 7.5 troy ounces of scrap karat per liter of acid and stuck with it. (The exception is sterling silver, of which, much more goes into a liter. And not to mention it is a liter of different acid!) But then again if you cannot tell the difference between sterling silver and karat gold, you are in the wrong business.

I have found that you talk to chemists like a chemist, and you talk to laymen like a layman. I always try to break things down to the lowest common denominator to make it less prone to error because the guy usually sticking his hands in the bucket usually doesn't give a damn, so he has to get it. And that is why I come up with simple parameters when needed.

 

[anachronism]

I have found that you talk to chemists like a chemist, and you talk to laymen like a layman. I always try to break things down to the lowest common denominator

OK!! I know my place then

 

[Lou]

If you want the full treatment, read into activity coefficients. His reference has to deal with empirical observations pertinent to karat gold. Colloquially, I call it "crowding" and it oft occurs with solutions containing several elements with species often of different valencies.

When I would prepare silver nitrate, it was not uncommon to have crystallizing solutions over 1000 g/L with no free nitric.

Platinum even I have had at 800 g/L

 

[4metals]

Lou,

Picture this; you are at a client (a refiner) speaking to the owner and he tells you his guy in the back is having trouble with a lot he is processing. So he asks you to go back and talk to the guy, help him get the gold out. You walk in and there's the head refiner, purple fingers, knuckles, and even the back of his hands are purple. He's wearing his standard work clothes, a stained white tee shirt with the arc shape from the top of his large belly stained to match his hands, and his jeans have small holes from melt splatter from mid thigh down to his shoes. He sees you coming and slips in a huge chunk of dip before you get to him. When you get to him he gives you a tight lipped grin and turns his head and does a dip spit into a pail.

Oh, and you're wearing a suit!

You going to tell him about activity coefficients?