Palladium test with DMG

[sayf]

Hello guys, i got 1 kg of cut realy contacts, i handled them with 22% nitric acid to get rid of the copper. it took about 2 hours with me to get the clean beads only. After that i did a DMG test for the copper nitrate solution as described in the forum to make sure that no significant amount of Pd has dissolved.
After adding the DMG solution to the sample i got a black cloud which vanishes after a minute as shown in the pic. Is this normal ? What it indicates.
Thank you

 

[Yggdrasil]

Hello guys, i got 1 kg of cut realy contacts, i handled them with 22% nitric acid to get rid of the copper. it took about 2 hours with me to get the clean beads only. After that i did a DMG test for the copper nitrate solution as described in the forum to make sure that no significant amount of Pd has dissolved.
After adding the DMG solution to the sample i got a black cloud which vanishes after a minute as shown in the pic. Is this normal ? What it indicates.
Thank you

I wonder, are you meaning Stannous?
DMG should produce a fluffy yellow salt in contact with Pd.
How did you prepare your DMG?

 

[sayf]

I wonder, are you meaning Stannous?
DMG should produce a fluffy yellow salt in contact with Pd.
How did you prepare your DMG?

No i mean a DMG test, i prepared 50 ml of distilled warm water and added few flakes of NaOH then added a spoon of DMG and stirred well until the DMG is totally vanished.

 

[FrugalRefiner]

That's not what I would expect a DMG test to look like. As Yggdrasil said, palladium would produce a yellow precipitate. Yours looks brown to me.

Dave

 

[FrugalRefiner]

I posted just as you responded to Yggdrasil. It's probably the NaOH. NaOH will create precipitates with most metals. Cobalt, iron, and silver will all form brown precipitates. I don't use NaOH when making a DMG testing solution. It's very sparingly soluble, but enough dissolves for testing purposes.

Since you dissolved contacts, my guess would be silver. Test another sample by adding a drop or two of HCl or salt. If it forms a white, cottage cheesy precipitate, it's probably silver.

Dave

 

[sayf]

I posted just as you responded to Yggdrasil. It's probably the NaOH. NaOH will create precipitates with most metals. Cobalt, iron, and silver will all form brown precipitates. I don't use NaOH when making a DMG testing solution. It's very sparingly soluble, but enough dissolves for testing purposes.

Since you dissolved contacts, my guess would be silver. Test another sample by adding a drop or two of HCl or salt. If it forms a white, cottage cheesy precipitate, it's probably silver.

Dave

Thank you very much , you are right .
Should i denox the excess nitric by sulfamic before testing or precipitation ?
Also the beads now are on the hot plate since 2 hours in concentrated nitric acid but some of them hasnt dissolved yet, do you think thats platinum ?
Will it take too much time to dissolve the beads in hot concentrated nitric acid ?

 

[sayf]

I wonder, are you meaning Stannous?
DMG should produce a fluffy yellow salt in contact with Pd.
How did you prepare your DMG?

I posted just as you responded to Yggdrasil. It's probably the NaOH. NaOH will create precipitates with most metals. Cobalt, iron, and silver will all form brown precipitates. I don't use NaOH when making a DMG testing solution. It's very sparingly soluble, but enough dissolves for testing purposes.

Since you dissolved contacts, my guess would be silver. Test another sample by adding a drop or two of HCl or salt. If it forms a white, cottage cheesy precipitate, it's probably silver.

Dave

Well, i denoxed excess nitric with sulfamic acid and added the DMG solution to the nitrate solution but no precipitate or yellow sponge has formed, i did a stannous test for the solution and i got the result shown.i uploaded The photo of the original solution too