# Dissolve lead and tin only!



## jaun

A refiner told me he uses sodium hydroxide (lye) and hydrogen peroxide to dissolve lead and tin only.

Does any one know about this? GSP, Lou, Steve, Harold
Or is he taking me for a ride?

He also spoke about using sulphuric acid and hydrogen peroxide to dissolve base metal???????? 

If lye and peroxide dissolve lead and tin, that would make things much easier!


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## Lou

No, he's serious.

Base with additions of peroxide is effective, giving you plumbate anion.


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## semi-lucid

Lou

Is it possible to then recover the tin and lead from the sodium hydroxide? Is this practical?

J


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## Lou

Yes, it can be done. Easiest to just precipitate as the hydrous oxide, and calcine with carbon. That ought to give you lead with tin floating on top. Just guessing here!


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## Buzz

In respect to the Lye and Peroxide solution
What would be a good ratio mix?

Regards
Buzz


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## jaun

He told me you add the peroxide slowly to the lye solution until all the lead is dissolved, I guess the same as hcl-cl where you ad the bleach little by little.

The stronger the peroxide the better.
We’ll have to experiment and see what ratio works best. 

I don’t know if there is any danger in this process, so please be careful. 8)


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## jeneje

Hello all, I know this is a very old post, but I am having prolbems with lead and tin in my solutions. I have tryed all the standard ways but still come up with lead and tin. Can the senior members here comment on this process and maybe give some insite on the dangers and correct amounts to use.

Thanks
Ken


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## machiavelli976

jeneje said:


> Hello all, I know this is a very old post, but I am having prolbems with lead and tin in my solutions. I have tryed all the standard ways but still come up with lead and tin. Can the senior members here comment on this process and maybe give some insite on the dangers and correct amounts to use.
> 
> Thanks
> Ken



Hi there !
If I am somehow in a hurry and I have to use nitric acid for digestion , my best catch is to use a stainless steel basket , hanged about one inch above the bottom of the beaker.
This way the SnO2 and fine lead drops leaving the bulk of pins (or whatever else) pretty clean for perpetual digestion.
The net i use for the basket have about 0.3 mm holes and some fine gold is passing thru obviously .
After digestion , only a slight rinsing above the same beaker would give you the gold clean enough to be dissolved further in AR.
The method is good for thick plating mostly. The light yellow pins will give to you very fine gold , easy to escape from the net.
The recovering of the fallen gold is another story and I'm still experimenting .You should try a boiling in HCl , but not before a good rinsing with tap water.


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## amosfella

I'm guessing the sodium hydroxide is mixed with water first...


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## samuel-a

amosfella said:


> I'm guessing the sodium hydroxide is mixed with water first...



sure.
This is your catalyst.

a solution of 50% NaOH with small addition of 30% H2O2 really works fast.
Stay safe, this is the most important thing.


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## eeTHr

I wonder if someone could use the standard grocery store 3% peroxide, if he didn't use water, but just the peroxide, with it's 97% water, to make the lye solution?


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## wct0415

So in the case of sterling silver knives where the stainless steel blade have been soldered in place, removing the blade with heat to melt the solder and allow the blade to fall out and dissolve the tin/lead with a solution of 50% NaOH with small addition of 30% H2O2. Will this solution affect the silver in any way or can the sterling be processed with 50/50 nitric and H2O. I think that I read in Hoke's book that HCL with H2O can be used to dissolve lead into a salt. Sounds like 50% NaOH with small addition of 30% H2O2 could be used to remove both the tin and lead. Any advise as to a better method would be greatly appreciated. Still trying to learn before jumping in with both feet.


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## solar_plasma

Those knives are often filled with sand and bee wax. This should be removed first, since bee wax in conc. NaOH especially if warm will make soap after some time. I never got soap from waxes, when I intended to, but shaving soap as an example is made of stearin acid (candles).


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## Evan2468WDWA

I was doing a Google search on C. M. HOKE and I found something related to this topic. 

http://books.google.com/books?id=oKLmAAAAMAAJ&pg=PA372&dq=C.+M.+HOKE&hl=en&sa=X&ei=owvDU9uYE8XUiwLpkoHoAQ&ved=0CCwQ6AEwAw#v=onepage&q=C.%20M.%20HOKE&f=false

Apparently if you heat up the caustic you don't need hydrogen peroxide.


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## necromancer

Evan2468WDWA said:


> I was doing a Google search on C. M. HOKE and I found something related to this topic.
> 
> http://books.google.com/books?id=oKLmAAAAMAAJ&pg=PA372&dq=C.+M.+HOKE&hl=en&sa=X&ei=owvDU9uYE8XUiwLpkoHoAQ&ved=0CCwQ6AEwAw#v=onepage&q=C.%20M.%20HOKE&f=false
> 
> Apparently if you heat up the caustic you don't need hydrogen peroxide.




there are dangers with hot caustic as with hot sulfuric.
it will eat organic matter away fast (skin is organic) best to try other methods or use all necessary personal safety gear.

a quote from Geo:



Geo said:


> ""Use some calcium hydroxide. It will convert the tin oxide to a hydroxide which is soluble in water. After mixing in the Ca(OH)2 and giving enough time for the conversion (30 minutes or longer) the tin will dissolve in water and can be rinsed out.""
> 
> ""You can buy calcium hydroxide at most grocery stores. It's called "pickling lime".""



not sure if this will dissolve the lead too ?

EDIT: spelling/grammar.


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## solar_plasma

Link please.

This seems to be completely teared out of its context, since this is about tin *oxide* (which of them?) and not tin. Though it looks interesting.


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## Geo

That's a quote from a different forum about tin oxide (metastannic acid).


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## necromancer

this post was brought back to life with a response 3 years to the day after it was needed.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=4998#p213131

i took it as an extension of removing tin / lead from solution. 

the OP was in 2009, then bumped in 2011, and again in 2014

did i not remember the definition of "Plumbate" correctly ?
and does my quote of geo's method conflict with something ? i did give credit where credit is due !!


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## solar_plasma

No, it's just that this is about tin oxides and not metallic tin. So it can't be used to dissolve metallic tin from boards.

Nevertheless, this method is interesting in other contexts. Thanks for mentioning it.


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## necromancer

the real thanks goes to geo

not sure how many tin coated / soldered boards you have but a hot sand bed works to get samples off the boards


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## Evan2468WDWA

necromancer said:


> there are dangers with hot caustic as with hot sulfuric.
> it will eat organic matter away fast (skin is organic) best to try other methods or use all necessary personal safety gear.


Thanks for the warning. If I do it I'll be careful.


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## necromancer

great, 

safety is something we all strive for.

it is one of the most important factors, it is always published on the top of all other methods for a good reason.

no one wants you to be harmed by the teachings here. there have been some scary stories posted in the past.

as one of the members has in there sig line.

"you cant fix stupid, stupid is forever"


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## bswartzwelder

One drop of NaOH to the eyes leads to permanent blindness. One drop of NaOH to blue jeans leads to a hole after they are washed. Anyone trying this needs proper safety gear.


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## DNIndustry

there is a process using Titanium and fluorboric acid i to remove tin/lead solder
very interesting.


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## bswartzwelder

This seems like it might be a good way to get rid of solder on circuit boards. I just don't know how it would work if the solder contains silver. Won't be trying this until after the spring thaw. Was wondering if there is any way to know how much solder could be dissolved in a gallon of this? Also, does this work quickly or should I put a bucket of it next to my AP bucket and sit back for a couple of days?


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## MarcoP

Yes interesting, but do you know how to dispose of it? I don't and if you do and would like to share would be a bonus. I stop my self from thinking about it because because it, availability and price.

There are other known ways to do it, pick one or more and study them in details.

Edit: as a general rule I always try to go for manual, mechanic or cold-acidic ways.


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## bswartzwelder

Earlier in the thread, a 50% solution of NaOH was recommended. It has been many years since I have had a chemistry class, but I have recently read that a 50% (w/v) solution is made by adding sufficient water to 50 grams of NaOH to bring it to 100 ml. A 50% (w/w) solution of NaOH is made by adding 50 grams of NaOH to 50 grams water.

I know I'm probably mixing apples and oranges, but doesn't the molecular weight of NaOH (40) enter into the equation somewhere? I'm going to have to do some serious digging to find my old college chemistry books. I guess my question is: When we mention a 50% solution, how do we know if we are talking of weight to weight ratio or weight to volume ratio?


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## MarcoP

I think, since NaOH's solubility in water is 1090g/L then I should use about 500g/L to produce a 50% concentration.


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## solar_plasma

% in chemistry is always weight percent, if nothing else is mentioned.

So 50% is 50g NaOH per 50g water.

Often it is easier to work with a concentration defined in mol: 1M NaOH would be 39,997g NaOH in 1 liter solution. About 12,5M NaOH would be 50wt%.

Why is it easier? Now, if you have used 1liter 12,5M NaOH dissolving tin and each mol of tin will use 2 mol NaOH, then you will have 6,25 mol tin or 741,9375g of tin in solution at the point of complete reaction, which ofcourse never will be reached in a slow reaction. Try to calculate this with wt%, - good luck :mrgreen: 

So even you don't want to use sophistcated chemical formulas, it might be worth thinking in mol and you will be able to calculate stoichiometric amounts in your head.


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## goldsilverpro

http://www.handymath.com/cgi-bin/naohtble3.cgi?submit=Entry


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## MarcoP

Then, if I understand correctly, it needs to be used a saturated NaOH solution.


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## g_axelsson

goldsilverpro said:


> http://www.handymath.com/cgi-bin/naohtble3.cgi?submit=Entry


Good link, I put it on the wiki. I'm going to check the rest of the calculators when my current work period is over. 80 hours in 8 days means not a lot of idle time, but a lot of money in the coffer.

:mrgreen: 

Göran


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## bswartzwelder

Thanks for the replies. I purchased 8 pounds of NaOH some time ago. When it arrived, it was in 4 two pound bottles. Makes it rather easy to make a 50% solution. Two pounds of NaOH and 2 pounds of water. As a youngster, I was taught "a pints a pound the world around". Not necessarily true, but makes it easy for mixing things up. At any rate, I'm sure it will be accurate enough for removing lead and tin. I plan on using about an ounce or 2 of the 35% H2O2.


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## solar_plasma

Have all skin and whole face protected, this concentrated NaOH is etching really fast and deep, the first 10 seconds you even don't feel any burning. Therefafter you will already have a lifelong scar, where the drip has hit you.


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## bswartzwelder

Thank you solar_plasma. I am well aware of how nasty this stuff can be. Just putting the powder into cold water can bring the water to almost boiling. As I said in another post, 1 drop to the eyes brings instantaneous, permanent blindness. There just aren't too many ways to recover or refine precious metals without using something nasty. I used some last year and 1 drop landed on my shoes. Next time I got them wet, there was a nice sized hole in them.


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## rajhlinux

I know I'm reviving an old thread... but any how, the magic formula of 50% sodium hydroxide and "a little addition" of 30% hydrogen peroxide means exactly what?

I'm assuming 50% sodium hydroxide means:
50 grams of 99% of pure sodium hydroxide mixed in 50 grams of distilled water

Same logic goes for 30% hydrogen peroxide, can easily buy 30% hydrogen peroxide premade.

Now what is the proper mix ratio between the two?
When people here are saying to add this with that, I don't like to eyeball things, that how you start a fire by playing around with the cool guessing game with extremely acidic toxic chemicals...

Can someone who has experience tell me what the proper weight ratio of how many grams or ounces is needed of 50% sodium hydroxide mixed with how many grams or ounces of 30% hydrogen peroxide. (At least provide a legitimate estimate, no one here should play the guessing game of trial and error with such chemicals.)

Also does this "50% sodium hydroxide and 30% hydrogen peroxide" solution will attack the copper base?

Yes, I need to have the copper nice and clean and untouched since I am prototyping a PCB and I need to remove the "Tin" from the PCB which was used as an "etch resist".

Much appreciated, thanks.


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## canedane

Yes, I need to have the copper nice and clean and untouched since I am prototyping a PCB and I need to remove the "Tin" from the PCB which was used as an "etch resist".
This helps us a lot to understand what your goal is.
Hot lye (20%)and 80-90 celcius water(80%) will dissolve the solder, but it will take the paint on your board as well.
I do not remenber how fast it goes but i will guess 20-30 min.
I see no reason to use hydrogen peroxide.
Try a sample before you take your importen board.
Lye will destroy your eyes, skin and lungs, specially hot lye!
Take care.
Henrik.


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## Lino1406

The available nitric acid tin removers, remove tin moderately quickly as SnO2. The concentrations
are stepped between leaving a thin tin layer to bright copper surface


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## geedigity

When I manufactured circuit boards in the 1980's, I seem to remember using 30% to 35% hydrogen peroxide to remove the tin (not sure if there was lead also) coating that was placed over the copper to make traces. After etching the boards using an ammoniacal spray etching system, I soaked the boards in the H2O2 to remove the tin so only the clean copper traces remained. That is what I remember, but it was so long ago that possibly I am mistaken.


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