Non-Chemical Melting and what it means

[Macleight]

Thank you GoldSilverPro and Butcher. You have answered my question.

 

[Macleight]

I actually want to recover the lead and the tin, as well as the other metals. This is why my idea was to separate by gentle heating, as these base metals have much lower melting points. But, as illustrated by the lead oxide, the addition of oxides, chlorides, nitrides might change the melting point by quite a bit, nearly 500 f in the case of PbO. This topic does not seem to be covered in other places, because people typically don't want to recover the base metals, which is why I asked directly, after a fair bit of searching. I am continuing to read about the properties of each of the metals I believe I have in solution or precipitated at this point.

I'm in virtually no danger. I handle hazardous chemicals often. I actually get paid to do it. Thank you for your concern.

Thanks to GSP and butcher for answering my questions.

 

[Lou]

So remind me, what exactly are you trying to do? Separate base metals by melting point or else sublimate them away?

 

[Macleight]

I have a solution that right now is dominated by solder. I know a fair amount of it is lead and tin, because that's what solder is. I know there was dissolved silver in solution, that precipitated out when I added the tap water to dilute the HNO3. I assume it is silver chloride because there is chlorine in the water. This is why I assume there is also lead and tin in their chloride form.

So my idea was to separate them first by filtering and washing, then heating. If I heat very gently, I should get tin first, then lead. The rest of the stuff that is left after this I could process again.

According to butcher, this will not work. Fractional distillation of metals is not really a thing. This was essentially my first question.

More broadly, academically even, my second question was, why not? The answer, also from butcher, lies in the way the metals alloy together. Not an answer, but the example he gave was gold forming a colloidal solution with tin, drastically lowering the melting point. Learning exactly why this happens is why I am still reading, learning and experimenting.

The answer to "what are you trying to do" was yes, separate by melting point. Again, the answer seems to be no, don't try this. I'd prefer not to sublimate them away. I'd like to separate and capture each one. Hoke tells me how to get rid of the tin and lead and stuff if I want to save precious metals. I can do this at my leisure. But she simply discards them after that. I know they are essentially worthless. I want them for the fun of it.

 

[FrugalRefiner]

I actually want to recover the lead and the tin, as well as the other metals. This is why my idea was to separate by gentle heating, as these base metals have much lower melting points.

Macleight, what you're missing in what members have been trying to tell you is that molten metals are, in general, excellent solvents for other metals. There are exceptions to this. For example, lead and zinc do not alloy well, so if you have a mixture of the two, you can heat it to a temperature above the melting point of lead but below the melting point of zinc and effect a pretty good separation. There are a few others like this, but they are the exceptions.

If you want to try a little experiment to see things for yourself, get some tin and some lead. You should be able to find some fishing sinkers made from each metal. Be sure to do this outside or in a fume hood as the lead fumes are hazardous. Melt some of the tin in a melting dish. When it's molten, add a lead sinker into the molten tin. Be sure the lead is not wet by heating it well before adding it to the tin. Any moisture could cause a steam explosion which could throw molten tin everywhere. You will see the lead dissolve into the tin, even though the temperature is below the melting point of the lead. Sorry, but it just won't work.

I'm in virtually no danger. I handle hazardous chemicals often.

If you believe that, you might want to consider a different hobby. Every good refiner KNOWS they are in danger every time they work at recovering and refining precious metals.

Dave

 

[Macleight]

Macleight, what you're missing in what members have been trying to tell you is that molten metals are, in general, excellent solvents for other metals.

I'm not missing it. I asked and you told me. Thanks! Someone else asked what I was trying to do, so I tried to say it a different way.

Sorry, but it just won't work.

I believe you. Thanks for telling me.

I'm in virtually no danger. I handle hazardous chemicals often. If you believe that, you might want to consider a different hobby. Every good refiner KNOWS they are in danger every time they work at recovering and refining precious metals.

Dave

I suppose it sounds cavalier in text. I have a very healthy respect for these chemicals, I am well aquatinted with many of them, I know my way around an MSDS, and I take precautions to protect myself. I have lots of PPE, I have checked that it will work with the vapors I expect to produce, everything is done inside a controlled environment. Thank you for your concern.

 

[necromancer]

i read & studied this forum for 2 years before trying to recover from electronic scrap. (hint hint)

 

[Lou]

I understand better.

The answer to your questions "can you fractionally distill metals and if no, why not?"...

1.) Yes, you can fractionally distill metals and separate them from one another in limited circumstances. It is done every day, some commercial examples being the production of high purity zinc, which may easily be distilled, or the separation of mercury from other low-volatility elements by high vacuum distillation.
2.) specific to your application, the answer is a resounding no for reasons brought up by other members--gold is well soluble in most transition metals and forms a variety of alloys. Lead and tin solders are effective solvents for gold and the gold would need to be recovered and refined hydrometallurgically.

Lead will boil at or around the melting point of platinum (1760 or so), so it would be effective for removing lead from platinum. Lead could potentially be removed from boiling gold, but that would be best left as a mental exercise.
Tin has a large liquidus range and will boil at 2602*C while gold boils at 2970*C. If one were zone refining iridium, this would be feasible.

Another consideration is that some metals are difficult to separate despite great disparities in melting/boiling points. One example would be removing iron from Ir or Ru; most siderophilic elements tend to have complex interactions with other transition metals that lead to surprising results.

Additionally, it is possible to recrystallize one metal from a molten metal solvent by varying temperatures and/or pressures. Again, unless other options have failed, generally this is best left alone.

Just to clear it up, gold does not form a colloidal solution with tin unless it is gold chloride reacting with stannous chloride in the well known Purple of Cassius test (which forms Sn(IV), gold-tin complexes, and gold nanoparticles responsible for the purple coloration). Please refer to the phase diagram for binary Au-Sn alloys.
Also, no metal sublimates so far as I know (some metalloids will). Some compounds, usually oxides of various metals may be solids and have considerable vapor pressures without being in the liquid state. One dangerous example is osmium tetroxide, OsO4.

 

[MarcoP]

i read & studied this forum for 2 years before trying to recover from electronic scrap. (hint hint)

Oh well that's right. After one year I'm just getting the gist of it, while I halted PM recovery.

 

[Macleight]

i read & studied this forum for 2 years before trying to recover from electronic scrap. (hint hint)

Ok. I started digging around 6 months ago. Read Hoke and Vols 1 and 2 once through, now going back again.

Lou, fascinating post. Thank you!