Dropping or getting metalic Sn

[Maurice]

Hello everyone.

I'am not a chemist, but I do feel like I have picked the wrong profession. I love chemistry .

I was hoping that someone would be able to help me make sense with the following. I wanted to turn my soldering wire into powdered tin and silver. And I have read quite a number of articles and watched a lot of video's on reactions of metals with different acids and thought that it shouldn't be hard to get what I wanted. Below I have described the materials I started with and the process that I walked through. All this was done outside.

Material:
50g of solder wire (97% Sn and 3% Ag)
HCL 33.4% rest is of-course H2O
Gloves
Safety goggles (covering both eyes like snorkeling goggles)
and a mouth piece

Goal
Turn the silver and tin into a metallic powder.

Process
I cut up the soldering wire in small pieces and placed them in a proper flask (250ml Erlenmeyer). Added enough HCL to cover the solder (about 1cm) . Placed it on a electric hot plate and set to low to medium heat. After a couple of minutes small bubbles where forming and the solder was slowly turning dark grey/black. I left it there for a couple of days. Turning the heat off when I wasn't home and adding HCL when needed. After all bubbling stopped I added a little more HCL to see if all the Sn was dissolved, no more bubbling so there was nothing more to dissolve and I was left with a clear liquid and a fine dark grey/black powder on the bottom of the flask.

Chemical reaction: 2HCl + Sn => SnCl2 + 2H

together with some silver powder on the bottom of the flask

I filtered the solution leaving me with a flask with SnCl2 and H2O and some silver powder in the filter. I washed and dried the powder and put it into a small flash (my first PM recovery ).

Now I wanted to turn the SnCL2 into Sn. Which "should" be simple by using iron or any other metal that is higher in the reaction series then tin would be.

Try - iron
I poured a little of the SnCl2 solution in a clean flask and added a piece of iron to it. It didn't take long for tin to be formed on the iron, but as soon as it formed the reaction did not continue. I have tried a hand full of different pieces of iron, all gave the same reaction. I even left some pieces of metal more then a day into the solution, but beyond the initial tin I couldn't see any new tin being formed. Now the solution should contain around 48.5g of tin, so I know for sure that there has to be more tin in the solution then I was seeing on the metal.

So this was not producing what I was expecting.

Try - aluminium
I know that HCl reacts violently with Al as I have seen on many video's and from my own experiments. So I added a very small piece (2 x 2 mm square) to a new flash with the SnCL2 solution in it. According to some sites this would produce ALCL3 and Sn as products.

Chemical reaction: 3SnCl2 + 2Al => 2AlCl3 + 3Sn

I noticed that the Al was attacked very quickly. Normaly with HCl you have a short time before the HCl can/will digest the Al because of the protective layer. The time between the Al hitting the SnCl2 and the reaction taking place was less then a second. The Al was covered (crusted) with Tin in a short 2 or 3 seconds creating a hissing sound, bubbling and steam. I read that this reaction generates a lot of heat (somewhere between 200 and 300 degrees Celsius). So I take it that the head evaporated some of the H2O to steam.

I also read that AlCl3 and water also react with each other according to the following formula

Chemical reaction: AlCl3 + 3H2O => Al(OH)3 + 3HCl

Producing HCl and Aluminium hydroxide.

And this should produce another reaction in which the newly created HCl will attack the just Sn metal again to form SnCl2 once more. So it seems that I have a loop in which the same reaction will take place over and over again. Until all the H is gone. I mean at some point in time there will not be anymore H in the solution as that is released when Sn is digested with HCl.

I took the crusted pieces of Al out of the solution and let it dry. It looks like I can crush the pieces with ease, haven't tried that yet.

Try - Electrolysis
I found another way to get Metallic Sn from SnCl2 by Electrolysis. I have not tried this yet.
I read that you get Metallic Sn at the Anode, but you also get SnCl4 at the Cathode. So not all the SnCl2 will be converted to metallic Sn which is one of the goals for this excessive.


Conclusions:
- Silver powder (or at least powder with a high concentration of silver can be obtained from digesting tin/silver solder in HCl. Still need to be refined further, but that is for the future.
- Getting metallic tin using normal Iron (Used a nail, a piece of computer housing metal, a couple of metal screws, a blade from a Stanley knife) doesn't seem to be working. All of these only produced a little bit of Sn and stopped shortly after.
- Using Al especially in bigger quantities will produce a lot of steam which can be dangerous.
- Anything higher in the reaction table is unwise to try out seeing how Al is reacting.


Questions:
- The Al that was placed into the solution is that completely converted into metal Sn ?
- Would this be a valid way of obtaining Sn powder or is there a simpler method ? (not counting buying tin powder).
- Why did the reaction stop with the Iron. Shouldn't the iron be replacing the Sn from the solution until there is no more SnCl2 to convert?

Thanks for reading. Any remarks, comments, warnings or anything else is appriciated.

 

[butcher]

Tin is a reactive metal, it will dissolve in the HCl acid to form a stannous chloride SnCl2 (a clear solution).
The silver will not dissolve in HCl and the small amount you had in your solder would just form a silver chloride, a whitish milky solution that can settle as a white fluffy powder.

Tin in the solution if diluted or sits for a long time, without more tin and HCl acid in solution (to keep the stannous chloride fresh) can hydrolyze, forming different compounds of tin, like SnCl4 with water you will form Sn(OH)4...

Iron in the acidic solution stannous chloride with an excess of HCl, can also form iron chlorides FeCl2 this with your stannous chloride, can give reactions of: 2FeCl2 + SnCl2 --> 2FeCl2 + SnCl4, here you would not see much tin precipitate (or cement from solution as the iron just reduces the tin to another soluble tin compound as the iron dissolved in the acid stannous solution...

Aluminum is very reactive metal to the acid in HCl it will dissolve violently, producing hydrogen gas (hydrogen gas with oxygen in confined spaces can become explosive), the hydrogen gas evolving from from your acidic solution, with it reaction on aluminum, as it reduces the acid (taking hydrogen from your acid basically neutralizing it to salts), with tin in this solution (as stannous chloride) and the acid being changed into hydrogen gases and aluminum chlorides your stannous chloride will lose its acid to keep it a stannous chloride ,and can also form stannic chlorides. Again leaving both aluminum and the reduced tin salt in solution, as a stannic chloride leaving you again with your tin in solution with the aluminum (basically just making a gooey mess or toxic solution to have to try and treat for safe disposal...
Basically after the hydrogen is gone from solution, you can have a solution of aluminum and tin chlorides and oxides or even hydroxides (with water)...


Tin is a metal that has many different oxidation states, and its chemistry can get very complex...

I cannot see these methods as a good way to get tin metal...

 

[kurtak]

First - do not dilute you HCl when dissolving your tin

then use zinc to cement out your tin

then wash/filter the tin powder (need to wash real good)

then dry the powder

then smelt with flux 50/50 borax/soda ash with a bit of fluorspar (to thin slag) 2 or 3/1 flux/tin (that's 2 or 3 times flux to tin)

pour to cone mold

Kurt