Unknown reason for NO2 production during aqua regia

[VanMarco]

hello.
So today i finally made aqua regia for what i am refining. Ashed chips.
I did the following up until now.
Do a HCl bath for the chips to remove solder from legs.
Incinerate, ball mill, gravity separation.
Nitric acid boils to remove copper and other base metals.
when i did not see any visible metal, i did the aqua regia.
what is puzzling me, is that even after hours of simmering, and basically nothing other than fine sand and silicon die pieces where left, I still saw a light veil of NO2 fumes being produced. I did add the nitric in 2mL shots at a time.
As of now, i have filtered the aqua regia and rinsed all well in the receiving container. I have kept all the solids and filter.
The AR has a textbook golden colour. I suspect i do have some free excess nitric in there.
So, it is normal to still get NO2 fumes even if it LOOKS like there's nothing left?

 

[eaglekeeper]

Do you have any Sulfamic acid available to denox with.

 

[Lino1406]

NO2 includes N+4. NO includes N+2, is converted to NO2 by air. Both are the product of oxidation by NO3-, which includes N+5. As long as you have oxidation, you have NO2

 

[Yggdrasil]

hello.
So today i finally made aqua regia for what i am refining. Ashed chips.
I did the following up until now.
Do a HCl bath for the chips to remove solder from legs.
Incinerate, ball mill, gravity separation.
Nitric acid boils to remove copper and other base metals.
when i did not see any visible metal, i did the aqua regia.
what is puzzling me, is that even after hours of simmering, and basically nothing other than fine sand and silicon die pieces where left, I still saw a light veil of NO2 fumes being produced. I did add the nitric in 2mL shots at a time.
As of now, i have filtered the aqua regia and rinsed all well in the receiving container. I have kept all the solids and filter.
The AR has a textbook golden colour. I suspect i do have some free excess nitric in there.
So, it is normal to still get NO2 fumes even if it LOOKS like there's nothing left?

Even if you can't see it, there may still be minute amounts of metal left.

 

[eaglekeeper]

So today i finally made aqua regia for what i am refining. Ashed chips.

Those bonding wires are so small, unless they are in a mass you probably won't see them...especially the RAM BGA type IC's.

 

[VanMarco]

so i guess i save those solids and filter for a successive batch, as now it seems to me that it would be excessive to put again a fresh batch of aqua regia for a very tiny amount. What I found odd is how long it would take to dissolve so little metal. I do not have sulfamic acid, i do have urea though.

 

[eaglekeeper]

so i guess i save those solids and filter for a successive batch, as now it seems to me that it would be excessive to put again a fresh batch of aqua regia for a very tiny amount. What I found odd is how long it would take to dissolve so little metal. I do not have sulfamic acid, i do have urea though.

I know you see the use of urea all over YouTube, but it's not really effective in denox'ing. Also, in the right conditions you could be producing Urea nitrate and it's something you don't want to get surprised with.

Sulfamic acid is the accepted compound to denox with. A lot of hardware/tile companies should carry it.

 

[Yggdrasil]

so i guess i save those solids and filter for a successive batch, as now it seems to me that it would be excessive to put again a fresh batch of aqua regia for a very tiny amount. What I found odd is how long it would take to dissolve so little metal. I do not have sulfamic acid, i do have urea though.

How much is it?

 

[VanMarco]

yes, i do know urea is not the best. the solution is like 400mL thereabouts. I don't think there is massive amounts of nitric left, as i don't do arbitrary amounts of hcl/hno3, but always add a bit of nitric at a time. with solid metal/visible metal it's easier to gauge. but it's always 2ml at a time so even if some is left, won't be much.

 

[Yggdrasil]

yes, i do know urea is not the best. the solution is like 400mL thereabouts. I don't think there is massive amounts of nitric left, as i don't do arbitrary amounts of hcl/hno3, but always add a bit of nitric at a time. with solid metal/visible metal it's easier to gauge. but it's always 2ml at a time so even if some is left, won't be much.

I meant, how much undissolved solids were there?

 

[J.Najam]

I know you see the use of urea all over YouTube, but it's not really effective in denox'ing. Also, in the right conditions you could be producing Urea nitrate and it's something you don't want to get surprised with.

Sulfamic acid is the accepted compound to denox with. A lot of hardware/tile companies should carry it.



View attachment 56708

Is there any alternative to Sulfamic for deNOxing Nitric? I see Urea is not the correct procedure for the same and Sulfamic isn't easily available locally? Any other name this acid might have? I'll try to look out for that too.

Thanks

 

[J.Najam]

Is there any alternative to Sulfamic for deNOxing Nitric? I see Urea is not the correct procedure for the same and Sulfamic isn't easily available locally? Any other name this acid might have? I'll try to look out for that too.

Thanks

Is this information correct? can it be used for the same if Sulfamic isn't available?

 

[Yggdrasil]

Is there any alternative to Sulfamic for deNOxing Nitric? I see Urea is not the correct procedure for the same and Sulfamic isn't easily available locally? Any other name this acid might have? I'll try to look out for that too.

Thanks

Best is to not use too much Nitric, easier and cheaper

 

[Yggdrasil]

View attachment 56733
Is this information correct? can it be used for the same if Sulfamic isn't available?

No

Sulfamic acid has the formula:
H₃NSO₃

You have Google, use your imagination man

 

[J.Najam]

Best is to not use too much Nitric, easier and cheaper

I completely agree. Nothing better than as suggested ^. Having said that, how would we know by a little heat evaporation that there is no more nitric in solution if we suspect that there may be a few MLs of extra addition?

 

[J.Najam]

use your imagination man

How is this suggested safe in practice? It may take experienced folks like yourselves years and years of knowledge and practice..

 

[Yggdrasil]

How is this suggested safe in practice? It may take experienced folks like yourselves years and years of knowledge and practice..

Are you just throwing out suggestions and asking, what about studying and checking for facts in stead of just throwing out random questions?
Here you were looking for Sulfamic Acid and Google will give the formula, you suggested Sodium bisulfate, why and where did you get that idea?
Check the formulas of these they are just vaguely similar, but that say nothing if they can do the same task.
Use your imagination on where you can find Sulfamic, names and places are different in all countries.
Do a Google search and so on, pick up the phone and call around to tiling businesses, what ever works for you.

Another thing is that if you are not grossly over adding the Nitric, you do not need to deNOx it.
Just add SMB in increments and the Gold will drop and redissolve until the Nitric is spent.
Or add a Gold button(best), piece of Copper or something until the reaction stops and go from there.

All these procedures are in here, just search and study.

Edit to change tone.

 

[J.Najam]

Here you were looking for Sulfamic Acid and Google will give the formula, you suggested Sodium bisulfate, why and where did you get that idea?

I didn't suggest anything per se, check out the image I shared it says "Sulfamic acid alternatives" and Sodium Bisulfate is the result I got. I read earlier on this forum that, that was not the correct solution. Hence, to double check the same I posted it here.

Are you just throwing out suggestions and asking, what about studying and checking for facts in stead of just throwing out random questions?

Not throwing out any suggestions, just have an intent to learn and clarify before any mistake could be made on my end. I'll just keep searching and studying before posting any questions.

 

[Yggdrasil]

I didn't suggest anything per se, check out the image I shared it says "Sulfamic acid alternatives" and Sodium Bisulfate is the result I got. I read earlier on this forum that, that was not the correct solution. Hence, to double check the same I posted it here.


Not throwing out any suggestions, just have an intent to learn and clarify before any mistake could be made on my end. I'll just keep searching and studying before posting any questions.

Ok.
I see that part now.
Sorry about coming on so strong.
This is completely out of context, so of course google won't give you a correct answer for this.
Search for products containing Sulfamic acid or just use plain sense and not overuse the Nitric in the first place.
If you don't find it, there are two alternatives, the method in Hokes book, evaporate, or not use more than needed.

 

[Yggdrasil]

I didn't suggest anything per se, check out the image I shared it says "Sulfamic acid alternatives" and Sodium Bisulfate is the result I got. I read earlier on this forum that, that was not the correct solution. Hence, to double check the same I posted it here.


Not throwing out any suggestions, just have an intent to learn and clarify before any mistake could be made on my end. I'll just keep searching and studying before posting any questions.

I did a few searches for you.