Metastannic Acid Experiment

[geoffbosco]

I know this is an old thread, but I have some tin paste (possibly lead paste as well) to deal with.

After incinerating the paste to get tin oxide and redissolving in HCL, the form of tin salt in solution is a chemically a bit different the garden variety stannous chloride. My question is: does the tin oxide hlc salt have similar properties and uses as stannous chloride, or will another process need to be done in order to use it as a valid testing solution?

Just curious as I am very frugal and if I don't have to pay extra for a source of tin to make stannous testing solution it would be very satisfying to my inner cheapskate.

 

[Lino1406]

(Chemistry lesson) Nop, stannic tin does not act as stannous tin. Actually stannous tin turns to stannic on operation (reduction)

 

[Rreyes097]

I know it's been a long time since this post, but i was just wondering what other people were coming up with in answers to the blue goo problem. And I thought back to when I first encountered it. I was living in the Bay Area in the heart of silicon valley. I had started to do my own backyard refining. And I ran a batch that had this hideous blue paste that was holding alot of my gold! I was pissed! So I left the filtering process alone for the night. The next day I checked out the filter, and saw that the liquid had finally gone thru but that paste was pretty thick on the filter. So I set it out in the sun to dry, wondering what to do with it. After it had dried, it looked like dried mud, all curled up and split apart and kinda burnt looking. So I crushed it up even more and stuck it in a plastic jar ready to shelve it. Then I got to playing around with the powder seeing what might desolve it. Alcohol, acetone, hot water, paint thinner, MEK...nothing really did anything to it. And then I got around to some sulfuric acid I had. Not wimpy electrolyte, industrial strength. I got a small beaker of it and set it out in the sun and went and got my powder. When I finally got back out there, the sulfuric was pretty well warmed up by the sun. But I sprinkled my yukky blue powder into it and WOW! the blue powder just kinda swirled and disappeared into solution and my gold just floated on top or sank to the bottom! So I grabbed that beaker and poured it thru another filter and there was my gold! The blue goo had just washed thru. I was so happy! Actually, there was alot more gold in there than I had thought. And it looked so good there in the filter w/o that crap. So, thats my old story of the blue goo and I've stuck with it ever since. I have gone on here to find other methods of dealing with it, but this was easiest in my opinion.

So many condradictions in these answers. Sounds like everyone has a way to do it that works. But I'm so information overloaded that I'm not sure where to go. I'm not working with foils but actual precipitated gold. Not sure how is the best way to get my gold back. I tried to read everyone of those posts but I still don't know which way to go.

 

[Lino1406]

So many condradictions in these answers. Sounds like everyone has a way to do it that works. But I'm so information overloaded that I'm not sure where to go. I'm not working with foils but actual precipitated gold. Not sure how is the best way to get my gold back. I tried to read everyone of those posts but I still don't know which way to go.

To dissolve tin dioxide there is the alkali + heating way; HCl + zinc way. 1st one dissolves tin dioxide as is, 2nd one reduces to tin++ and then dissolves

 

[Rreyes097]

To dissolve tin dioxide there is the alkali + heating way; HCl + zinc way. 1st one dissolves tin dioxide as is, 2nd one reduces to tin++ and then dissolves

How does one do the first of the two choices?

 

[Lino1406]

How does one do the first of the two choices?

Look at the 1st post of this thread

 

[Rreyes097]

Look at the 1st post of this thread

Put the gold bearring Metastannic into the reaction vessel.
Add water to just above the material about 1/2 inch.
Add 1/2 teaspoon of lye.
Heat solution(DO NOT BOIL) you will see a reaction of the lye change colors it will cheese up to a fluff and then change to a brown material and settle to the bottom.
While warm decant and filter the solution as much as you can. It will be Brown.
Add water to the remaining solution NOT MUCH.
Add HCL to the solution, this will change to a yellow / green.
Decant and filter - your trapped gold will be free and settle in the filter. Use the same vessel and filter as before to decant in.
This post?

 

[Yggdrasil]

Put the gold bearring Metastannic into the reaction vessel.
Add water to just above the material about 1/2 inch.
Add 1/2 teaspoon of lye.
Heat solution(DO NOT BOIL) you will see a reaction of the lye change colors it will cheese up to a fluff and then change to a brown material and settle to the bottom.
While warm decant and filter the solution as much as you can. It will be Brown.
Add water to the remaining solution NOT MUCH.
Add HCL to the solution, this will change to a yellow / green.
Decant and filter - your trapped gold will be free and settle in the filter. Use the same vessel and filter as before to decant in.
This post?

Yes that is what he was referring to.

But you should read further and you will notice the information becomes modified.
It ends up with what most recommend.
Roast and dissolve in HCl.
The NaOH route seem to have a possibility to dissolve some Gold.

 

[Rreyes097]

Awesome thank you. I did read pretty much everything that was posted on that thread. But it just managed to further confuse me. But thanks.
Quick question though. Does it matter if your gold is in the form of foils or powder? Because mine is currently powder having been precipitated?

 

[Yggdrasil]

Awesome thank you. I did read pretty much everything that was posted on that thread. But it just managed to further confuse me. But thanks.
Quick question though. Does it matter if your gold is in the form of foils or powder? Because mine is currently powder having been precipitated?

Does not matter much, but roasting should not be done on Gold salts since they can volatilise and create high losses.

 

[Rreyes097]

So am I ok i roast?

 

[Yggdrasil]

So am I ok i roast?

That should be ok.
Just follow the steps in this thread.

 

[Rreyes097]

I missed this question from Topher here in this tread back when he first posted it - so he sent me a PM asking the same question (which I answered in a PM)

Because I provided a link to this thread as part of my answer in another recent question about stannic tin - I thought I would up date this thread with the answer I sent Topher in a PM - that answer (to Topher) was as follows ------------

Hokes page 71 says --- "If you still have some tin paste, left over from an earlier experiment, try the effect of sulphuric acid upon it. . . It dissolves it, whether dilute or concentrated."

But it doesn't --- not really - though it does have "some" effect on the stannic tin it does not actually truly dissolve it - it more or less brakes it down into an ultra fine colloid - much the same as NaOH as explained here by Chris :arrow: Dealing with gray metastanate gunk

So - if there is just a "small" amount of stannic tin - it will put it into suspension long enough for the foils to settle & then decant it - washing "most" (but not all) off

Or - it makes it fine enough that much of it (but not all) will pass through a filter (can't use a paper filter as the sulfuric will ash the paper)

So - although it will help to "reduce" the amount of stannic tin (if you started with a "small" amount of stannic tin in the first place) it wont eliminate all of it

The reason I know this to be true is that I tried it (about 4 or 5 years ago) on some stannic tin (a LOT of stannic tin - like a couple cups full) that had "some" (very little) "ultra" fine foils tied up in it

So I figured I would (as suggested by Hokes) "dissolve" the stannic tin away with sulfuric --- I started using concentrated sulfuric - it did not dissolve the stannic tin & the foils where so fine that by the time they settled - most of the tin did as well - leaving a somewhat cloudy ( stannic tin in suspense) solution

So I tried diluting it --- same result - thought maybe I just didn't use enough sulfuric to dissolve all the tin (stannic) so added more sulfuric --- same result - tried time with stirring - as well as heat - as well as adding more sulfuric (to concentrate) & then diluting again

After a about a week of messing with it & using up a gallon of sulfuric I ended up with my ultra fine foils still tied up in a bout 1 1/2 cups of stannic tin (so reduced the stannic tin by about 1/2 cup & about 3 gallons of sulfuric waste (from diluting)

With incineration (reduction roasting actually) & as long as you do your roasting to completion (convert all the stannic tin to tin oxide) you can then "eliminate" ALL the tin with the HCL wash/leaching

Conclusion --- if you want to "insure" you have got rid of the tin - incinerate & treat with HCL

Kurt

So I have some precipitated gold with static tin, not very much of it but enough to discolor the gold powder. Do you think I should use the sulphuric acid or roast it? And when you say roast it do you mean simply putting a torch to it? Or heating up a pan with the gold and stannic tin in the pan?

 

[Yggdrasil]

So I have some precipitated gold with static tin, not very much of it but enough to discolor the gold powder. Do you think I should use the sulphuric acid or roast it? And when you say roast it do you mean simply putting a torch to it? Or heating up a pan with the gold and stannic tin in the pan?

Read this thread!!

 

[Rreyes097]

I did! But after rereading it for the third time I thought maybe the sulfuric acid might be a good choice for me since it's only a small bit of stannic acid I'm dealing with. And I wasn't sure what they meant by roasting Open flame or in a pan with heat up below it?

 

[Yggdrasil]

I did! But after rereading it for the third time I thought maybe the sulfuric acid might be a good choice for me since it's only a small bit of static acid I'm dealing with. And I wasn't sure what they meant by roasting Open flame or in a pan with heat up below it?

There is no such thing as static acid, it is stannic.

Next, I suggest you read the thread until you understand what it says.

If you don't understand it, I'd suggest you find another hobby, we cant do your work for you.
Errors happen to all of us, but if you don't understand what you do and why, you risk doing something really dangerous and then worsen it by doing the wrong thing on top of that.

It is all in here, read and read again until it is clear, make notes if you have to.

 

[theitalianhenchman]

I've read the thread; in one place is said to heat up to 2500F° (+-1300C°); but tin liquifies around 230C°... what is the right way? How can one manage to make it "red hot" without liquifing it? I guess a stainless steel pan on an eletric plate would work?

Just wondering..would this route be quicker and create a lot less waste instead of the AP method?

 

[Yggdrasil]

I've read the thread; in one place is said to heat up to 2500F° (+-1300C°); but tin liquifies around 230C°... what is the right way? How can one manage to make it "red hot" without liquifing it? I guess a stainless steel pan on an eletric plate would work?

Just wondering..would this route be quicker and create a lot less waste instead of the AP method?

Metastannic acid is not metallic so it won't liquefy.
Matastannic acid is a Tin Oxide H₂SnO₃.
But when that is said I think 1300C is too much, it should be enough with a red hot 500-650 C.
I have not done it myself so please chime in if I'm wrong.

 

[Yggdrasil]

I've read the thread; in one place is said to heat up to 2500F° (+-1300C°); but tin liquifies around 230C°... what is the right way? How can one manage to make it "red hot" without liquifing it? I guess a stainless steel pan on an eletric plate would work?

Just wondering..would this route be quicker and create a lot less waste instead of the AP method?

Tha AP method will not create Metastannic acid, but it is slow.
One can speed it up by doing it hot 50-70 ish C.

 

[Saddiq NG]

I have been doing some low grade pins in HNO3(nitric), as we know it creates Metastannic Acid and it is hard to get the gold foils. I have found an easy way to rid the Metastannic and its works for me. Here is the process i used today along with pics, The steps are as follows,

Put the gold bearring Metastannic into the reaction vessel.
Add water to just above the material about 1/2 inch.
Add 1/2 teaspoon of lye.
Heat solution(DO NOT BOIL) you will see a reaction of the lye change colors it will cheese up to a fluff and then change to a brown material and settle to the bottom.
While warm decant and filter the solution as much as you can. It will be Brown.
Add water to the remaining solution NOT MUCH.
Add HCL to the solution, this will change to a yellow / green.
Decant and filter - your trapped gold will be free and settle in the filter. Use the same vessel and filter as before to decant in.

Hope this helps someone.
Ken

update; Using the procedure above will put gold into solution, just done a test with stannous and its positive, Done a bigger amount and it works for a leach solution on Metastannic for micro gold removal. More tests are needed to confirm.

Nice experiment man thank you.
I have encountered this metastannic acid so many times, I once cried because of its problem.
I have also discovered a simple way to avoid with an easy method I will like to share here. But unlike yours, this method will prevent it from forming by eliminating the tin before reacting the pins, or PCBs in nitric acid.
To do this simply cover the the pins or PCBs in water, the add a few drops of nitric acid 67% to the solution, then give it some heat and a few hours (at least 1 hour). Assuming you covered your pins in 400ml of water, you will need only 25ml of nitric to do this.
As the solution is heated with time, it will turn from clear color to green. Sometimes the metastannic acid can even precipitate out.

The acid will be strong enough to attack the less reactive metals like tin while the more reactive metals from copper above are not attacked, therefore the acid is so weak it will not strip any gold foil. When you're comfortable you've eliminated all the tin, pour off and discard the waste solution.

If you do this properly, when you add nitric acid to eliminate base metals, no metastannic acid will form.