Dissolving gold plated fingers and others in Nitric .Help Me

[razvanflorin]

:arrow:

Hello ! Today i have started dissolving some gold plated fingers in nitric acid

( 5090 gr of fingers )
( 5 L Nitric acid (54%)
( 3 L H2O)
( 230 ML H202 35% ) For nox gasses

i have used an fume hood and tryed to get back the NO2 Into the nitric acid used to dissolve the fingers. the problem is that they didn't dissolved yet ...
how much Nitric do i have to add more ?
Does it is a problem that i have used H2O2 ?

Thanks in advance !

P.S. I Know that most of you will tell me that A/P Proccess is better, but for me is more expensive and time waste.

Kind Regards - Razvan

 

[Barren Realms 007]

You will probably need about another 30L of 30% nitric. Give or take.

When you are new at this it is best to do about 50g-100g of material to find out how much it takes and then you can do your calculations on the approximate total of solution you will need. Until you get more experience it would be best for you to do a bunch or small process and not screw up rather than one large batch and have to ask a bunch of questions.

Good luck.

 

[patnor1011]

30 liter? What make you think so Frank?
5090g of fingers does not mean 5090g of copper. As far as I know PCB does contain about 30% Copper (some more some less) and even then Nitric will not dissolve all copper present in fingers as most of it is sandwiched in between layers.
If I would have to guess I would estimate that another 5l should do the job comfortably. I may be wrong but 35l of 54% HNO3 on 5kg of fingers looks way too much to me.

 

[Barren Realms 007]

30 liter? What make you think so Frank?
5090g of fingers does not mean 5090g of copper. As far as I know PCB does contain about 30% Copper (some more some less) and even then Nitric will not dissolve all copper present in fingers as most of it is sandwiched in between layers.
If I would have to guess I would estimate that another 5l should do the job comfortably. I may be wrong but 35l of 54% HNO3 on 5kg of fingers looks way too much to me.

Oooopppppsssss.


I thought it said pin's not fingers. Well duh. I guess that is what I get for working 60 hour weeks in the sun and rain. 8)

Thanks for catching that Pat.

Strike my comment due to heat stroke.

 

[jason_recliner]

Does it is a problem that i have used H2O2 ?

This is not a problem, in fact it is beneficial.
As you know, H2O2 will reduce the amount of NOx gasses released. By keeping them in solution, it follows that it will stretch your nitric further.

 

[razvanflorin]

thanks you all for the answers i will come back with the results after i will finish thanks you very much !


Kind Regards - Razvan