Have you ever noticed gold disappear during a nitric leach?

[9kuuby9]

Hello guys!

I recently stumbled upon something very interesting,I noticed that the nitric solution is green, which make me think that their is something wrong here!
I was leeching base metals (with nitric acid) from some foils I have recovered; and after a day i noticed that they disappeared completely.
Which brought me tho solve this matter. So as I was doing something else (dissolving some silver) i noticed that silver chlorides where forming in the silver nitrate solution. So I figured out that My distilled water tank has been mixed whit tap water.
Meaning that it's possible to dissolve gold with tap water and concentrated nitric acid (around 50%-60).

And Their was no hydrochloric acid left overs or something of that sort: I ran out of hydrochloric acid 3 weeks ago, and a week ago I cleaned all my glass equipment in my lab.

I tested the solution whit stannous chloride and guess what?; it tested positive! (the solution dissolved around 15g of gold foils; keep in mind that this reaction took over a day witch is surprisingly quite short. I don't know if this could happen/manage with gold filled scrap)

Quite a mystery I had their, So I wanted to share this whit you guys :mrgreen:

 

[NobleMetalWorks]

Does your water have a lot of chlorine or other things like hydrochloric acids to insure it's "drinkability"?

Scott

 

[9kuuby9]

Does your water have a lot of chlorine or other things like hydrochloric acids to insure it's "drinkability"?

Scott

Well it definitely contains salts such as (metal)chlorides, They add bleach to ensure it's drinkability.

But in very very small quantities, as 0.001%-0.005%


Maybe a build-up of salts or chlorides in the pipes may have caused this.

 

[NobleMetalWorks]

I was acting on behalf of a friend, attempting to get a housing permit pushed through the city so that he could build a house. The problem was with the water pressure, it had to be a certain amount so that the fire department could hook up to it. The reason the pressure was low was because one of the cities water pumps was pumping arsenic in amounts too high to be safe for humans.

Point is, as shocking as it may seem If you put city water into your solution you have no idea what you really are adding. You can only control what is in your solution if you control everything that goes into it. City water does strange things, I only use it for washes, etc.

Scott

 

[9kuuby9]

yes, Indeed it sometimes might even cause skin allergies if just used as for the purpose of washing.

I guess we'll have to test the water before using to be sure of instead getting information that might have been played with.

Sometimes the water companies try to use the cheapest options since the average won't notice it.

As I like to say, Cheap is dangerous!

 

[kurt]

Was HCL used at any point in the original recovery of your foils (to remove tin &/or AP process)

If so & you did not incinerate your foils before the nitric treatment then you in effect made a forum of AR due to traces of HCL residue

Kurt

 

[9kuuby9]

Was HCL used at any point in the original recovery of your foils (to remove tin &/or AP process)

If so & you did not incinerate your foils before the nitric treatment then you in effect made a forum of AR due to traces of HCL residue

Kurt

No I haven't used HCL at any point, I mechanically removed the pins from the fiber CPU's and the processed them with nitric because I ran out of HCL.

At some point the beaker was blue due to the copper nitrate and then it turned into a green solution which is copper chloride.

 

[butcher]

You can test for chlorides with a silver nitrate solution, which would form a milky solution or a silver chloride precipitant if chlorides were involved.

Palladium can also give other colors to nitric acid solutions, DMG could be used to test for Palladium, yellow precipitant if positive.

Colors of solutions can be indicators, but judging what is in a solution by colors can fool you, as sometimes other metals not expected may give a solution the color and trick you.

 

[kurt]

Hmmmm - interesting - are you distilling your own water - I ask because if you are & you don't de-chlorinate it first you are not getting rid of the chlorine.

When distilling chlorinated tap water what you really end up with is purified water (free of bacteria & minerals) that is still chlorinated --- thats because chlorine evaporates at a lower temp then water so the chlorine evaporates first & then condenced into your catch tank & then the water evaporates & is added to the chlorine.

Also buthcher is right about solution colors - they can be an indicator of what is in solution but not an absolute - nickel in nitric will show green color

Kurt

 

[kjavanb123]

All,

I have some input about this issue, I have tried PCI slots before using tab water to produce the dilute nitric acid, and i could see no gold foils at all, but today I used distilled water and now gold foils are sitting on the bottom and be clearly seen. Amazing difference.

Kj