Experiment 41: Growing Sulfur Crystals

In this experiment, I recrystallized garden sulfur (90% pure) to make pure sulfur crystals that gleam in the light and are a light yellow color.  First, I acquired a solvent for sulfur.  Since sulfur dissolves well in toluene, xylene, and carbon disulfide, I picked the most common option--xylene.  My xylene came from paint thinner (it listed xylene as an component).  To separate the xylene from the methanol and acetone also in the paint thinner, I mixed equal volumes of water and paint thinner and vigorously shook.  This should be done outside, as the vapors are unhealthy.  I poured the mixture into a graduated cylinder and let it settle for 15 minutes.  The xylene, which is insoluble in water, floated at the top, while the acetone and methanol remained in the water layer.  I syringed off the xylene and ended up with ~45mL from three 50mL batches of paint thinner.

Then, with my solvent collected, I began the recrystallization.  I placed the xylene in a beaker with a stir bar and some impure sulfur and heated it on medium heat on my hotplate.  I also had a beaker full of snow water resting on top of the xylene beaker to act as a crude condenser and recover xylene vapors.  The whole experiment was done outside.  The xylene shouldn't boil, or else vapors will go everywhere and escape the crude condenser setup in large quantities (unhealthy).

With the sulfur dissolving, I placed another beaker with a small amount of xylene (no sulfur) on the hotplate to warm.  I also put a third clean beaker on the hotplate with a coffee filter on its top.  Just as the xylene began to boil, I poured the prewarmed pure xylene through the filter in the third beaker.  This warmed the filter and the beaker to prevent sulfur from crystallizing immediately on contact with the cold surfaces.  Then, I filtered the dissolved sulfur mixture through the filter.

Once it finished filtering, I removed the filter and covered the beaker's mouth with tape to prevent losing xylene vapors.  I then wrapped the hot beaker in towels to slow its cooling.  This helped the crystals to grow more slowly, which makes bigger crystals.  Once it cooled completely, I decanted off the xylene (which still had some dissolved sulfur in it) and scraped the sulfur crystals onto a coffee filter to dry.  After the first batch was dry, I tried using them as seed crystals for a second and third batch of crystals, which seemed to make larger, prettier crystals.  The resulting pure, shiny piles of sulfur crystals were quite beautiful.