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 doesnt exhibit any color changes. None of the three materials dissolve into water.