whats going wrong

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whats going wrong
« on: 06/11/2008 23:56:54 »
hey, i am trying to melt sulfur into its pure yellow form.
but every time I try it only stays at its 3rd stage of melting,which is the almost solid stage. how can i get it to go to its complete yellow form?



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whats going wrong
« Reply #1 on: 09/11/2008 14:57:13 »
As a chemistry student I remember making brown/red 'plastic' sulphur and that if it's left to its own devices would revert over time to the yellow crystalline form. I found this too:

The S8 molecule is stable, and exists in solid, liquid and gaseous sulphur. Two crystalline forms compete, orthorhombic α-sulphur and monoclinic β-sulphur. Below 96, the orthorhombic form is more stable, but it is a fairly narrow thing, and conversions between the two forms are slow. α-S has a density of 2.07 and melts at 113C. β-S has a density of 1.97 and melts at 119C. Each melts to a straw-yellow liquid of density 1.808 called λ-sulphur. If the liquid is cooled slowly, needle-like monoclinic crystals form. When the temperature falls below 96, these crystals slowly change to orthorhombic microcrystals, which is shown by their becoming cloudy. If the liquid is heated further, at about 200C it darkens to a reddish color and becomes viscous. The S8 rings are thermally broken, and recombine to form long chains, called μ-sulphur. The dark color is due to the free valences at the ends of the chains. If this dark sulphur is suddenly cooled by being poured into water, it becomes a rubbery mass of tangled chains. This was called amorphous sulphur, but is really a kind of glass. On standing, it eventually reverts to S8 and crystallizes. S6 molecules make rhombohedral crystals, which is called (I think) γ-sulphur. There is apparently also an S12 molecule.

Hope that helps.