I forgot to neutralize! , help me please

[dpgold]

Not a big problem , double the size of you aqua regia solution by tap water because gold loves to precipitate from diluted not concentrated solutions ,
You can eleminate the nitric using many ways :

1- nitric elemination by urea : (not recommended)
heat your aqua regia for couple minutes until it is warm
add urea to the aqua regia, small spoon firstly a strong fizzing will start, wait until its finished then stir slowly
Add another small spoon if nitric is still there, strong fizzing will happen again wait until its finished and stir slowly again, repeat those stips until you notice that the fizzing is very weak, there are many videos explaining the nitric elemination by urea

2- nitric elemination by sulphamic acid :
same as above but replace urea with sulphamic acid

3-nitric elemination with evaporation.
4-nitric elemination with iron sulphate (recommended becausr This way will both eleminate the nitric and precipitate the gold)

after you eleminate the nitric filter the solution and drop your gold with SMB or iron sulphate

So there are three things to do precipitate any lead from AR, denox (get rid of excess nitric) and precipitate. If I use sulphamic acid that will precipitate lead and denox the solution. ? Sulphuric acid will do the same?

 

[Geo]

So there are three things to do precipitate any lead from AR, denox (get rid of excess nitric) and precipitate. If I use sulphamic acid that will precipitate lead and denox the solution. ? Sulphuric acid will do the same?

No. Sulfuric acid will precipitate lead(II) sulfate but does nothing to remove excess nitric acid.

 

[Geo]

I've seen people refer to Hoke's when talking about evaporating and additions of HCl to denoxx solution. I'm not sure everyone grasps the scope of what's been said. The solution may have to be evaporated to a syrup. This is a very delicate process and needs a fair amount of finesse. It is a tiny step from syrupy to a burned crispy crud. Harold_V recommends adding a small volume of sulfuric acid to the solution before starting. Sulfuric acid is difficult to evaporate to dryness. As sulfuric acid becomes more and more concentrated, the more resistant to boiling or evaporation it becomes. It's not impossible to evaporate to dryness after adding sulfuric acid but it is much more difficult.

 

[Shark]

No. Sulfuric acid will precipitate lead(II) sulfate but does nothing to remove excess nitric acid.

This is why I use it. It makes the lead easily filtered out. Usually only a small amount of lead so I can still use sulfamic if it is needed to denox. It goes something like this…… add sulfuric and drop lead, cool and drop silver, denox as needed, filter to perfectly clear. Drop the gold. You can now cement or process for pgm’s or add to stockpot.

 

[dpgold]

thank you Geo. While I was asking these questions (a few hours ago) I put some vintage gold plated circuit boards in AP (which I will label with solder) and I noticed it was pretty fast acting, some of the foils already started to move in a few hours. The lead or solder was gone. My concern is with how do I recover the foils if there is lead, the foils can become tiny pieces. Theoretically tin and lead and other things go in the solution and everything else which has not dissolved should be filtered and washed in the filter?

 

[dpgold]

This is why I use it. It makes the lead easily filtered out. Usually only a small amount of lead so I can still use sulfamic if it is needed to denox. It goes something like this…… add sulfuric and drop lead, cool and drop silver, denox as needed, filter to perfectly clear. Drop the gold. You can now cement or process for pgm’s or add to stockpot.

Thank you,

 

[dpgold]

I have just found this in the Hoke's book: Premixing Aqua Regia - In Hoke’s day it was common to premix aqua regia in a fixed ratio, then to combine it with the metal. While others have developed similar techniques, GoldSilverPro has championed the cause of adding nitric acid in increments. It is far better to add only the amount of nitric needed to perform the task than to add too much and have to deNOx after the metals have been dissolved.

how do you know when there is enough nitric, how long do I wait before I add more or not add further?

 

[Geo]

thank you Geo. While I was asking these questions (a few hours ago) I put some vintage gold plated circuit boards in AP (which I will label with solder) and I noticed it was pretty fast acting, some of the foils already started to move in a few hours. The lead or solder was gone. My concern is with how do I recover the foils if there is lead, the foils can become tiny pieces. Theoretically tin and lead and other things go in the solution and everything else which has not dissolved should be filtered and washed in the filter?

Lead chloride is water soluble as long as the water is hot and can be removed by adding it to hot water. It is also soluble in concentrated HCl. After collecting all the solids left behind, boil in water or add fresh HCl to remove lead chloride. When cool, lead chloride will look like long needle shaped crystals. Adding sulfuric acid creates a fluffy white powder of lead sulfate that settles quickly and is easily filtered out of solution.

 

[dpgold]

Lead chloride is water soluble as long as the water is hot and can be removed by adding it to hot water. It is also soluble in concentrated HCl. After collecting all the solids left behind, boil in water or add fresh HCl to remove lead chloride. When cool, lead chloride will look like long needle shaped crystals. Adding sulfuric acid creates a fluffy white powder of lead sulfate that settles quickly and is easily filtered out of solution.

Thank you again, this is really useful, all these details. I took out the test pieces last night and washed them in a separate bucket. How long shoul I wash it to get rid of any lead chloride and deal/dispose with the wash from the solution safely?

 

[Yggdrasil]

Put the “gunk” in the bottom in a beaker and boil it while stirring. Then filter it. All lead residue should be out by then. The filters can then be leached in your preferred way.

 

[Martijn]

how do you know when there is enough nitric, how long do I wait before I add more or not add further?

By watching the reaction in your beaker. And the changes you observe when adding something. You have to have some basic knowledge of chemical reactions to start performing processes. What does it do when hot, cold, dilute, concentrated, mixed with other.. etc. etc. first look up the reaction in theory, and then test if the expected outcome will occur.
The acquaintance tests in hokes book help a lot. It's basically a way to study the different properties of acids and substances and how they react to each other before you throw all kinds of stuff stuff in a beaker and hope it wont explode in your face. Small beaker, small explosions big beaker.. well you can guess the rest.
Take your time and do small tests first.

 

[dpgold]

By watching the reaction in your beaker. And the changes you observe when adding something. You have to have some basic knowledge of chemical reactions to start performing processes. What does it do when hot, cold, dilute, concentrated, mixed with other.. etc. etc. first look up the reaction in theory, and then test if the expected outcome will occur.
The acquaintance tests in hokes book help a lot. It's basically a way to study the different properties of acids and substances and how they react to each other before you throw all kinds of stuff stuff in a beaker and hope it wont explode in your face. Small beaker, small explosions big beaker.. well you can guess the rest.
Take your time and do small tests first.

The test was about how to get rid of the lead (Pb) and now I see that I did get rid of it (learning experience) but now is mixed with some of the gold which comes off in this old AP.(now when I don't want the gold plating to come off-Murphy's law) I understand that this lead chloride will dissolve in hot water or in concentrated HCL (which I can filter) or....

 

[Yggdrasil]

Simple. Don’t mind the lead. It is in the AP as dissolved PbCl. Let it be there until you have filtered the foils from it, then drop it from the liquid with Sulfuric. Don’t make a problem from something that is not. If you over treat it, it will/can become a problem.

 

[Shark]

Lead(pb) is one of the easiest metals to remove from AP or AR. If you follow good steps when using AR or AP the lead(pb) will follow the waste stream and not your gold. If it does happen to make it into your AR, it is still one of the easiest metals to remove at this stage.

 

[dpgold]

Simple. Don’t mind the lead. It is in the AP as dissolved PbCl. Let it be there until you have filtered the foils from it, then drop it from the liquid with Sulfuric. Don’t make a problem from something that is not. If you over treat it, it will/can become a problem.

Ok, thank you all, so I should treat it as other base metals in the AP process but when I want to filter the foils I now have that gray powder which will remain in the filter when I filter the foils from AP.
So I had one dedicated small bucket with previously used AP but which did not have contact with any Pb. After dissolving the circuits it dissolved some AP from the boards. Then I took the test boards out and washed them in a separate bucket with water and that is where I have observed the grey powder. I am assuming this is the step which precipitated the Pb and other stuff beside copper which confused me.

 

[Martijn]

Grey powder after filtering foils from AP, are you sure it's lead and not CuCl1? Lead is not very common in solder anymore. Only old electronics have it.

 

[Martijn]

If it is lead, rinse the filter with hot water, if its copper chloride, rinse the filter with HCl.

 

[Geo]

Copper(II) chloride (CuCl2) will create Copper(I) chloride (CuCl) when you add water. CuCl is a white fluffy powder that is normally colored green from remaining CuCl2. When you rinse CuCl2, it rinses away any green color and leaves the white powder. Any dark colored solids will make it appear gray. The lead that comes at the end of a CuCl2 leach will be ground up crystals and look like a white powder. It does not dissolve well in cold water. It is easiest to remove after the dissolution of the gold foils and before filtering the pregnant solution. After the gold is dissolved and the solution has cooled, add 10ml of sulfuric acid. If lead is present, and it will be seeing as it's in all electronics that we would be interested in, a white cloud will form. After some brisk stirring, it will settle quickly. Keep adding sulfuric acid until no more white cloud forms. Lead sulfate actually filters relatively easily. Lead is a problem for jewelers in gold because it makes gold less malleable and more prone to cracking or breaking when being worked.

 

[dpgold]

Grey powder after filtering foils from AP, are you sure it's lead and not CuCl1? Lead is not very common in solder anymore. Only old electronics have it.

Yes, I did the test on some old electronics boards, I usually try to select materials, and the test was a separate batch with Pb solder boards

 

[billgold]

If I recall correctly, Hoke also discusses incremental addition of nitric acid when doing the digestion.