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It is common knowledge that tin melts at $449.5~\rm^{\circ}F$ and Lead at $621.5\rm~^\circ F$, and that when these are melted together you simply have an alloy.

What happens, or what product occurs, if you take pure lead to red heat ($1,400$ – $1,500~\rm^\circ F$) in a muffle furnace and cast in pure tin?

The mixture "Blooms" with somewhat small cubic crystals that, when scooped off the top into a receptacle, appears as a sulfur colored scoria that I was not able to re-melt into metal at even $2300\rm~^\circ F$.

I have a photo if I can figure out how to post it.

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    $\begingroup$ Must be some oxide. $\endgroup$ – Ivan Neretin Dec 30 '15 at 20:54
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    $\begingroup$ You're probably creating a toxic miasma: though that is below the boiling point of lead, some would evaporate. $\endgroup$ – DrMoishe Pippik Dec 31 '15 at 5:09
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    $\begingroup$ What is the material of the crucible you're using? $\endgroup$ – hBy2Py Jan 1 '16 at 0:14
  • $\begingroup$ I think you have insufficient reputation to insert images yourself. Post your photo to the image sharing service of your choice, and edit your question to include a link to it. One of the more established members of the community can then edit your post to include the image directly. $\endgroup$ – hBy2Py Jan 1 '16 at 0:15
  • $\begingroup$ You're all very kind. I'm using a ceramic dish to molten the metals and a clay crucible as a receptacle for the material I gently scrape from the top of the molten metal. I'm trying to understand you're instructions for posting a photo but it's over my head experience-wise. I can say that the "Bloom" occurs quickly and the surface of the molten metal is completely covered with the forming "Crystals" which are much brighter than the molten metal, so much so that they appear incandescent. $\endgroup$ – Howard Malone Jan 1 '16 at 17:08
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I think Ivan Neretin has given the right answer.

Any alloy between Sn and Pb melts at relatively low temperatures. You stated that the compound you fabricated did not even melt at 2300 °F. I have been looking at the stable lead oxides and tin oxides. The only compound of this set that has a melting temperature above 2300 °F is tin dioxide at 2970 °F.

Please note that I cannot be certain of this, as I only checked a small set of compounds I found to be the best candidates. It could be the case that you have created something more complex. (beautifully phrased by DrMoishe Pippik as a 'toxic miasma' :-) )

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