white precipitate formation in nitric acid bath of ceramic processors

[Pradeep Chaudhary]

i started with 2 batches of 36 ceramic processors
26 intel pentium in white bucket
10 486s in beaker
after breaking them i covered them with regular pure ground water
and then added 400- 200 ml nitric acid respectively in bucket and beaker
immediately white substance begun to form and after a night of reaction this is the result
now i want to know what is it and how to process it further
is it cement silver because silver bond wire dissolved in nitric could have cemented out immediately because of gold plated base metal contact pins??

 

[Yggdrasil]

Where did you find this procedure?

You should have used HCl, this is probably metastannic acid from Nitric reacting with Tin.
Clean them thoroughly by shaking them to dislodge all the white, remove and flush all parts til clean, water going into same bucket.
Put the pieces in another bucket. Metastannic acid is next to impossible to filter, that is why we avid it as much as possible.
Evaporate the liquid down to dryness, then roast the powder until glowing red.
You can then dissolve it in among other things NaOH, but to make sure there are no AgCl it's better to use HCl.
Your foils will now be accesible to dissolve as you wish.

 

[Pradeep Chaudhary]

Where did you find this procedure?

You should have used HCl, this is probably metastannic acid from Nitric reacting with Tin.
Clean them thoroughly by shaking them to dislodge all the white, remove and flush all parts til clean, water going into same bucket.
Put the pieces in another bucket. Metastannic acid is next to impossible to filter, that is why we avid it as much as possible.
Evaporate the liquid down to dryness, then roast the powder until glowing red.
You can then dissolve it in among other things NaOH, but to make sure there are no AgCl it's better to use HCl.
Your foils will now be accesible to dissolve as you wish.

nitric acid is frequently used to dissolve base metals

like in this video and many other videos people use nitric
by the way thanks for you reply
but roating the white powder mixed with ceramics is next to impossible
and i dont have access to naoh either
can i just cotton filter the whole solution and wash 2-3 times with hot water
and then dissolve everything in AR
is there any possibilty of silver cementing back due to other base metals present
or maybe leftover thermal paste is causing the white powder to form?

 

[Yggdrasil]

nitric acid is frequently used to dissolve base metals

like in this video and many other videos people use nitric
by the way thanks for you reply
but roating the white powder mixed with ceramics is next to impossible
and i dont have access to naoh either
can i just cotton filter the whole solution and wash 2-3 times with hot water
and then dissolve everything in AR
is there any possibilty of silver cementing back due to other base metals present
or maybe leftover thermal paste is causing the white powder to form?

There are tin solder there, and tin and nitric are not a good mix.

Youtube can kill, and at least lead you astray.

There are less then a handful of Youtubers recommended by this community, Owltech, Sreetips and Aquila are among them.

Yes, Nitric do dissolve base metals but also silver and most importantly it creates MetaStanninc acid in contact with tin,
and we hate metastannic tin because it creates a lot of extra work.

Another reason nitric is almost never used to dissolve base metals is that it is much more expensive than HCl,
actually quite a few members can't even find it in their countries.
NaOH is easy to get everywhere, I believe, but HCl is as I said better, it won't convert what may be there of AgCl.

If you can not rotate it, you will have to pick up a few in an other smaller bucket and rinse them there.

Your secondary problem is that the gold foils are mixed into the goop and you will not be able to access them
until it is dissolved, which means doing what I told you.

After everything is clean from the goop, you can add the pieces to AR if and only if its ceramic style CPUs.
They contain some bonding wires, most other don't.

Use the AR as follow:
Add HCl until the processors are covered, do this in proper borosilicate glassware, heat it until around 60-70 centigrade
and add Nitric in small quantities, stop when there is no more reaction.

Stir properly.
When no more reaction happens, add more HCl and try a bit more, if it has stopped,
you can remove the CPUs while spraying them with a spray bottle with water until clean.
When this is done, dilute it with some water and cool it down.
Now you can filter it until completely clear.

Add what ever precipitant you like to the now clear solution and let your gold drop.
Collect your gold and wash properly.

 

[speed]

There is no tin in ceramic CPUs.

It does look a bit like silver chloride but I'm unsure how you would have formed it with pure water and pure nitric. If theres no chloride present then you shouldnt have silver chloride.

It could be a number of different compounds but I would suggest it's from impurities in your acid/water rather than from the cup.

It is correct that you are better off going straight to AR with ceramics tho. Far too much iron in them for nitric!

 

[orvi]

Nitric won´t dissolve the gold from the brazing under the silicone. So for me, more steps and high consumption of precious nitric acid. Base metal to gold ratio for ceramic CPUs is very good, not very much metal to dissolve, unlike mid-grade pins etc.

To the white stuff... Honestly, nothing plausible comes to my mind. Aside of dirty nitric or dissolved silicon heat paste You say that it reacted overnight - but I don´t see any blue colouration from the copper. Why is that ? did you washed and decanted the copper liquid ? Or it did not gone blue-green at all ?

I think nitric acid is here to blame. But I may be wrong.

 

[Geo]

Nitric acid leaching of ceramic CPU's is recommended. Add a small amount of sulfuric acid to help the nitric acid attack the Kovar. 10 ml's per 1000 ml's is plenty. Kovar is very close to stainless steel in composition and nitric acid has a hard time attacking it. As "speed" stated, there is no tin in ceramic CPU's. If you are using ground water, there will be dissolve limestone in the water. To test, take a sample of your water and add a small amount of sulfuric acid and stir. If there is dissolved calcium in the water, a white precipitate of calcium sulfate will form. In your case, I believe you have formed silver chloride some how. Take the white solid and expose it to sun light. If it darkens the longer it's exposed, it is silver chloride without a doubt.

 

[Yggdrasil]

I stand corrected
Thanks for putting me straight, the Youtube bit still stands though.

 

[richoc]

You stated you used "clean ground water" well that is a wild card here.
You should be using distilled water so it as near pure water as you can get.

This white stuff kinda looks just like what is left as hard water deposits in the distiller my buddy runs on his farm.
Lime scale deposits.
See if white vinegar soaking of one part will effect the scale deposited on it.

 

[Pradeep Chaudhary]

View attachment VID_20220331_113049.mp4This is how it is in 10 486 batch little greenish but this soft powder is mystry

 

[PeterM]

View attachment 49316This is how it is in 10 486 batch little greenish but this soft powder is mystry

What is the solution HNO3? If it is and if there is TIN on the boards, use just created Metastannic Acid. Congrats, you just made a mess.

 

[richoc]

You totally cleaned them of any heat sink paste, some of the best paste I used when building
Custom PCs is 90% silver, but your silver should stay in nitric.
Spoon out a bit of the "white ooze" and put in another set of vessels.
See if soluble in water, vinegar(light acid), or nitric.

Pull out some of the processor chunks and see what has occur to them at this point.
Are the pins dissolving or not, has any of the inner parts been effected.
If the processor are not very effected at the point I would carefully wash them of the goo.
Dry them out well and start again.

Ok here we go in the way back machine to admit a screw up.
When I first tried a nitric strip of plated parts in water/nitric.
Used tap water not thinking about all the chemicals the city puts in it.
Well I got white substance looking much like you have there, coming out of solution and the more I tried to stop it the more I got.

 

[Pradeep Chaudhary]

Update:I tested thermal paste in same nitric and water and there was no color change
And I cotton filtered the solution
It turned from white to black
And there is much more white stuff left in the bucket.
And the pins are not soft yet,it means base metal is not dissolved yet
What should I do next?

 

[richoc]

Ok Once you clean all the processor chunks and do a final rinse and dry with distilled water......

You are at step one.( again)
Your scrap should now be free of any foreign unknowns.

The nitrc never got under the pins, and it could not effect the bonding wires in the CPU it self.

 

[Alondro]

There are tin solder there, and tin and nitric are not a good mix.

Youtube can kill, and at least lead you astray.

There are less then a handful of Youtubers recommended by this community, Owltech, Sreetips and Aquila are among them.

Yes, Nitric do dissolve base metals but also silver and most importantly it creates MetaStanninc acid in contact with tin,
and we hate metastannic tin because it creates a lot of extra work.

Another reason nitric is almost never used to dissolve base metals is that it is much more expensive than HCl,
actually quite a few members can't even find it in their countries.
NaOH is easy to get everywhere, I believe, but HCl is as I said better, it won't convert what may be there of AgCl.

If you can not rotate it, you will have to pick up a few in an other smaller bucket and rinse them there.

Your secondary problem is that the gold foils are mixed into the goop and you will not be able to access them
until it is dissolved, which means doing what I told you.

After everything is clean from the goop, you can add the pieces to AR if and only if its ceramic style CPUs.
They contain some bonding wires, most other don't.

Use the AR as follow:
Add HCl until the processors are covered, do this in proper borosilicate glassware, heat it until around 60-70 centigrade
and add Nitric in small quantities, stop when there is no more reaction.

Stir properly.
When no more reaction happens, add more HCl and try a bit more, if it has stopped,
you can remove the CPUs while spraying them with a spray bottle with water until clean.
When this is done, dilute it with some water and cool it down.
Now you can filter it until completely clear.

Add what ever precipitant you like to the now clear solution and let your gold drop.
Collect your gold and wash properly.

Conc. sulfuric is also good, if you know how the handle fumes (which can be captured and bubbled back into flasks of 20% or 35% H2O2, reforming dilute sulfuric acid and giving you more reagent). Tin sulfate is pretty soluble in acid solutions, and the sulfuric also helps sort silver-palladium from gold-platinum. Ag and Pd will dissolve in it, Au and Pt will not.

Less concentrated sulfuric will only dissolve silver, only weakly attacking Pd.

There is a method to dissolve Pd and other PGMs with 60% sulfuric and 0.1M NaCl heated to 125C for 10 hours which dissolves >99% of PGMs found in a ResearchGate paper. This might be good overall to split PGMs from gold, as well as dealing with the tin. The PGMs form chloride complexes, which reduce quite well afterward, and the tin remains in solution along with other base metals.

 

[Geo]

Update:I tested thermal paste in same nitric and water and there was no color change
And I cotton filtered the solution
It turned from white to black
And there is much more white stuff left in the bucket.
And the pins are not soft yet,it means base metal is not dissolved yet
What should I do next?

White powder that darkens in the light is silver chloride. Take a small sample of the white powder and add to it a little ammonium chloride. If it is silver chloride, it will dissolve. Add HCl back to the solution will precipitate white silver chloride.
WARNING: Always acidify any solution of ammonia and silver as soon as possible due to the danger of creating an explosive compound.

 

[Alondro]

White powder that darkens in the light is silver chloride. Take a small sample of the white powder and add to it a little ammonium chloride. If it is silver chloride, it will dissolve. Add HCl back to the solution will precipitate white silver chloride.
WARNING: Always acidify any solution of ammonia and silver as soon as possible due to the danger of creating an explosive compound.

Just like dissolving silver in conc nitric and 100% ethanol... when that solution dries and crystallizes, you tend to have a very bad day. Kind of like picric acid, which we had a bottle of in my old biology lab cabinet... that was crystalizing. Disposing of that without exploding ourselves was quite the experience.