is it necessary to dilute AR before precipitation
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It all depends on how much metal you have in solution. If you cleaned up the material you are refining with a leaching step and most of what you have in solution is gold, then it is not necessary, however if there was excess nitric in solution then it becomes advantageous to dilute it. We know little to nothing about what you are digesting or trying to accomplish so it is difficult to give a specific answer.
More detail from you will help you get better advice.
More detail from you will help you get better advice.
It also depends on whether there was silver in your feed material. A concentrated AR solution will hold a bit of silver in the solution, which will contaminate your gold. Diluting the AR causes the silver to precipitate before you filter and drop the gold.
Dave
Dave
I work on refining jewelry polishing bags 18 k gold
if dilution is not that necessary I prefer to precipitate without excess solution
I denox that free nitric
my steps are roasting the material completely
apply a magnet to remove vibrator stainless steel balls
crushing the material to fine particles
then I put it in aqua regia without the first hcl wash
if dilution is not that necessary I prefer to precipitate without excess solution
I denox that free nitric
my steps are roasting the material completely
apply a magnet to remove vibrator stainless steel balls
crushing the material to fine particles
then I put it in aqua regia without the first hcl wash
Unless you know for sure that your 18k dust and fines in the sweeps contains no silver, then do as Frugalrefiner suggested and dilute. I was amazed at how much silver chloride can be present in hot, concentrated AR resulting from processing karat scrap. Without dilution, it would be hard to know, that is until you begin washes with ammonia.
Nuwaysolutions
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One goal for precipitating gold is to get rid of the nitric acid in the AR. Boil down and refill with water several times should do the trick.
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Nuwaysolutions said:
There are many far more effective ways of getting rid of Nitric than that I promise.
You beat me to it Jon, http://goldrefiningwiki.com/mediawiki/index.php/Denoxing
Göran
Göran
Topher_osAUrus
Well-known member
diverwild said:
They already answered that a couple posts up. But...
If your material has silver, it benefits you to dilute it so the (usually) insoluble silver chloride will precipitate out of the now weaker acid solution.
It also helps if you were just a little bit heavy handed with the nitric additions, if you used WAY too much nitric, you need other methods of denoxx, I for one would not go with water additions if evaporating, but instead small HCl additions. Also make sure you have a little sulfuric acid in the mix if you do choose the evaporation technique for removing your excess nitric.
It also helps if you use SMB for your precipitant by keeping the SO2 gas in the solution to reduce the gold.
You CAN dilute the AR solution too much though, so 3-4x volume should be more than sufficient.
Distilled water, tap water, makes no difference in this case. Ice would probably be your best bet, honestly. But, it seems as if there is a lot of stuff you should read up on to know when and why to use the ice.
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Guys, he's asking about making less waste liquid. Depending how much he is doing, it's entirely possible that he would be better off not diluting the initial AR prior to drop.
Diver are you doing a lot of this gold or just very small quantities, can you let us know how much please?
Diver are you doing a lot of this gold or just very small quantities, can you let us know how much please?
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Thanks.
Do you do this amount in one or more AR solutions and how much volume of raw solution would you use for each?
Do you do this amount in one or more AR solutions and how much volume of raw solution would you use for each?
anachronism said:
One AR solution which I think weighs approximately 5 liters liters
concentrated HCL and nitric I thought this is important so all gold become soluble untill yesterday I read a fourm in which Harold said he could use one liter for nearly 500g of dissolved gold in it and he had to use ice to let all gold precipitated so tomorrow I plan on using one liter of AR for each process
if dilution has no positive effect on the process lets say it could make gold precipitate or settle faster or any other good benefit why would someone do it
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You can process in less liquid to start with as you rightly pointed out. 5 litres is too much, so yes you can take that down. Experiment with 1 litre instead of 5 litres and try that. If that works then go smaller.
Diluting 1 litre produces less waste than diluting 5 litres but that's just mathematics so I agree that reducing your liquid amount at outset is your first step. If you were to denox your solution completely, cool it, and once settled filter it to crystal clear then you will have very little silver left in the solution. Probably little enough to allow you to clean residual amounts of silver out of the precipitated gold powder using an HCl wash or two.
Good filtration is the key to this.
I would recommend experimenting as you will soon see silver chloride on your gold powder as a white fluffiness. My advice would be to try what I have suggested above. If you find you have small quantities of silver left, then there is nothing to stop you redissolving the gold in a very small amount of liquid- and then following the "dilute by three times" approach because diluting a couple of hundred cubic centimetres will produce way less waste again.
Jon
Diluting 1 litre produces less waste than diluting 5 litres but that's just mathematics so I agree that reducing your liquid amount at outset is your first step. If you were to denox your solution completely, cool it, and once settled filter it to crystal clear then you will have very little silver left in the solution. Probably little enough to allow you to clean residual amounts of silver out of the precipitated gold powder using an HCl wash or two.
Good filtration is the key to this.
I would recommend experimenting as you will soon see silver chloride on your gold powder as a white fluffiness. My advice would be to try what I have suggested above. If you find you have small quantities of silver left, then there is nothing to stop you redissolving the gold in a very small amount of liquid- and then following the "dilute by three times" approach because diluting a couple of hundred cubic centimetres will produce way less waste again.
Jon
The problem with processing burnt sweeps in aqua regia is the amount of gold that is retained in the ash sludge from poor rinsing. To get the most out of the sweeps you need to rinse them well. Fortunately the rinse waters is very dilute acid and it contains your gold that did not filter out of your digestion. You can either set up a glass still and boil off the water to make a concentrate of the aqua regia that the sweeps contained. If it's sunny and dry where you are consider a solar still for your dilute wastewater.
It is good practice to place a few drops of stannous chloride on your filtered ash. If the acid still contains gold it will indicate that to you.
I have 2 clients that have a large centrifuge made just to spin solutions down to avoid time consuming filtrations on sweeps. The problem is they have to add water and mix the sludge at least 3 times to get all of the retained acid from the sludge. So the volume creeps up from adding water before filtering or on the other end when the sludges retain too much value.
Why do you start in Aqua regia? If you did a first leach in nitric and distilled water you could also recover the silver. Once the silver has been through aqua regia it is much more difficult to get out the silver.
It is good practice to place a few drops of stannous chloride on your filtered ash. If the acid still contains gold it will indicate that to you.
I have 2 clients that have a large centrifuge made just to spin solutions down to avoid time consuming filtrations on sweeps. The problem is they have to add water and mix the sludge at least 3 times to get all of the retained acid from the sludge. So the volume creeps up from adding water before filtering or on the other end when the sludges retain too much value.
Why do you start in Aqua regia? If you did a first leach in nitric and distilled water you could also recover the silver. Once the silver has been through aqua regia it is much more difficult to get out the silver.
Dust, likely it may because the particles are small, but you are looking to leach out the silver not dissolve the gold. What percentage is the silver in the 18K alloy?
