Sulfur and Toluene: Growing large rhombohedral crystals.

Just a quick write up- I got many PMs and saw people asking about my sulfur crystals.

Pouring about 1L of cold toluene in a large vertical graduated cylinder (almost to the top), then added about 50-100g of fairly pure (at least 99%) sulfur flour. I sealed the top of the vessel with 2 layers of aluminum foil (the liquid must not contact the aluminum- Sulfur will corrode the aluminum).

I then insulated the bottom 2/3rds of the vessel, and put it on a hot plate. I attempted to use a heat sink on the top of the vessel, but it was not necessary. Airflow over the top of the vessel was created with a fan- The top of the vessel must be cooled.

Then, place the vessel on a hot plate, and tilt the vessel and hot plate a few degrees- This will assist convection and internal flow.

The hot plate was set for 50*C, and left for a few days. Over this time, convection occurred, and hot saturated toluene precipitated sulfur once it cooled.

The hottest liquid must not exceed 46*C, otherwise thin, prismatic crystals will have a chance of forming. The lower the 'hot' temperature, the slower the crystals will form, but the clearer they will be (most crystals will have inclusions of toluene, disrupting the crystal structure).

Large, single crystals are VERY possible, I just wanted super-pure sulfur (achieved by then heating the sulfur below it's melting point, as a powder, to remove all toluene). Lower temperatures, more convection, and purer ingredients will help.



Added quick note: Crystals shown here grew over a few days, at 40*C 'hot' in a 20*C room. The layer of white-ish crud at the crystal level is the floated particulate impurity in the sulfur flour, the junk at the bottom is the same (or maybe other other) impurity, once the sulfur has been pulled into solution and removed from that area.

[Edited on 7-24-2012 by Wizzard]

[Edited on 7-25-2012 by Wizzard]

Thanks for the method Wizzard!