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In this youtube video by chemicalforce: https://youtu.be/3cvUXW__QZ0

When he heats the lithium metal to metal fire point we see a yellow flame. When he brings the SF6 close it becomes green and when he touches it to the metal it sizzles red.

What is the reason for this?

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    $\begingroup$ Seems like this questions should be asked on Chemistry. $\endgroup$
    – march
    Commented Nov 17, 2022 at 18:18
  • $\begingroup$ For context, the reaction of interest is $8\mbox{Li}+\mbox{SF}_6\to\mbox{Li}_2\mbox{S}+6\mbox{LiF}$. Lithium fluoride is yellow-white; lithium's flame test colour, presumably showing due to the heat allowing $4\mbox{Li}+\mbox{O}_2\to2\mbox{Li}_2\mbox{O}$, is red. I'm hoping a chemist can explain the green. $\endgroup$
    – J.G.
    Commented Nov 17, 2022 at 22:24
  • $\begingroup$ The well-known crimson flame lithium flame test color is lithium atomic emission around 670.78 nm. The green is likely from sulfur or sulfur-containing flame species: there was air present in the demo. The yellow I assume is just from the bulk lithium burning. $\endgroup$
    – Ed V
    Commented Nov 17, 2022 at 23:37
  • $\begingroup$ @EdV I have seen boron burning green characteristically $\endgroup$
    – ChemEng
    Commented Nov 18, 2022 at 22:16
  • $\begingroup$ @ChemEng Sure, and barium and copper salts and some phosphorus compounds, e.g., en.wikipedia.org/wiki/Thiophosphoryl_fluoride , and likely quite a few other things. But, as a chemist who did spectroscopy, I really prefer seeing spectra obtained with spectrometers! ;-) $\endgroup$
    – Ed V
    Commented Nov 18, 2022 at 23:13

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