Bismuth Compound: Change Colors with Heat

[JGM_14]

I have this compound of bismuth that when it is room temp it is green and when it is hot it turns yellow then maroon (dark red). I prepared it by melting bismuth then stirring (while melted in air) until it turned into a green powder with grains roughly the size of granulated sugar or salt. the green was about this color ===>, the yellow the color of iron(III)chloride or solid sulfur, and the red this color===>but a little darker. When it was heated to red hot it formed a glasslike substance similar to obsidian (volcano glass)in color. That substance boils and leaves behind a substance that looks like carbon. The original powder can be dissolved into flint glass and exhbits the same color changes without the red at all (green then amber or yellow) when heated, but is clear at room temp. The black glass like material also dissolves into the same kind of glass but doesn't exhibit any color changes. None of the three materials dissolve into water.

 

[Navin A S]

It is likely that the compound you have is bismuth oxide or sulfide. Bismuth oxide is a naturally occurring compound with a characteristic green color, and it can turn yellow or reddish-brown when heated. Bismuth sulfide is another naturally occurring compound and it has a characteristic yellow color, which darkens to maroon with heating. Both compounds are insoluble in water, but soluble in flint glass. The black glass-like material is probably elemental bismuth that was formed when the original bismuth compound was heated to a high temperature. Elemental bismuth is insoluble in both water and flint glass.

 

[ravenprp]

Wow, that is really interesting! It sounds like you have discovered a unique property of bismuth compounds. The fact that it changes colors with heat is fascinating and could have many practical applications. Have you tried experimenting with different temperatures to see if the color changes are consistent? It would also be interesting to see if the color changes can be reversed by cooling the compound. Overall, your findings are impressive and I'm sure they will contribute to our understanding of bismuth compounds. Keep up the great work!