Sciencemadness Discussion Board

Allotropes of Sulpher

Wrecking Bereserker - 2-4-2019 at 08:28

I'm trying to make allotropes of sulpher but not getting it right these are steps i took help me through it
I tried to dissolve sulpher in CCl4 and heat to evaporate to produce sulphur crytals it didn't work
Then heated a new sample it until it melts and poured it into cold water wich made some tiny balls i don't quite sure what to do after that
Then i heated an another sample until it became sticky this is also an allotrope right?

12thealchemist - 2-4-2019 at 08:39

There are many allotropes of sulphur. Rhombic and monoclinic are the most common. Rhombic sulphur is stable at room temperature, and is the most stable allotrope. Monoclinic sulphur is only stable above 95.3°C, and can be prepared by crystallising sulphur at 100°C. Plastic or amorphous sulphur (μ-sulfur) can be prepared by pouring sulphur heated to above 160°C into water. It is unstable, and over a few days will slowly revert to rhombic sulphur.
λ-sulphur is the light yellow liquid formed when sulphur initially melts
π-sulphur is formed when λ-sulphur is allowed to sit just above the melting point for an extended period of time. It is a dark colour.
Trisulphur is present in hot boiling sulphur vapour, and is visible as a dark red gas.

Sulaiman - 2-4-2019 at 08:55

Sulphur is not very soluble in CCl4, 0.8 % w/w
Attachment: Solubilityofelementalsulfur.pdf (42kB)
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so you would have to make a saturated solution, filter it and DISTILL off the CCl4 as the fumes are a health hazard.

CS2 dissolves sulphur easily but is not cheap and its fumes are also undesirable.

I have grown sulphur crystals from sulphur dissolved in toluene,
but the solubility is also quite low, which means wasting valuable solvent (and polluting the air)
or distillation which is a nuisance to set up for a simple experiment.

woelen - 2-4-2019 at 23:01

Sulphur dissolves quite well in hot toluene, not in cold toluene. I once dissolved some sulphur in toluene, kept at around 100 C and then allowed the toluene to cool down slowly. I put the test tube with a saturated solution of sulphur in hot toluene in a beaker, which I filled with boiling hot water. I used a glass tea beaker, which is double-walled, with low pressure between the two glass walls. These beakers keep the liquid warm for quite some time. In this way, I could make nice shiny crystals of sulphur.

Tsjerk - 3-4-2019 at 06:40

I made some really nice slightly yellow needles of sulfur by crystallization from hot toluene.

12thealchemist - 3-4-2019 at 08:44

I've also recrystallised sulphur from toluene to excellent effect - it's fairly soluble in boiling toluene, far far less so in cold. And since toluene is impossible to freeze without LN2, you can chill it right down to squeeze out almost all the sulphur you do dissolve.