Melting sulfur

Solid matter that can be melted becomes thinner and thinner until it begins to boil and evaporate. You can try this on a piece of ice. Done? Now let’s see what happens if we melt sulfur.

First, prepare a glass of cold water. You will need that soon.

Then fill a test tube 1/3 full with powdered sulfur.

Gently heat the glass so that the sulfur just begins to melt. Make sure that the melt does not discolor, if possible. It should remain a transparent yellow.

Now heat a little more vigorously. The melt quickly turns deep red to black and becomes increasingly viscous. Soon you can even turn the glass upside down; nothing flows out anymore.

Then continue heating vigorously. The melt becomes somewhat more liquid and yellow vapor forms. It condenses as a solid, yellow substance on the test tube wall. Attention! Be careful and don’t let the steam ignite. Otherwise, you have to stop heating and cover the glass to extinguish.

Now pour the molten sulfur into the glass with the cold water. It hisses a little. You can see that the sulfur coagulates into a yellowish, transparent mass. Let cool for a few minutes, then remove the mass. Check their properties. Compare it with crystalline sulfur.

What happened?

In the beginning, everything corresponds to the melting behavior of water. If you let the clear yellow melt cool down, you will get solid, yellow sulfur again.

The red-brown melt forms a rubbery mass when it is suddenly cooled in cold water (it is called “quenching”). We speak of plastic sulfur.

The sulfur vapor that forms when the sulfur is boiled is, strictly speaking, sulfur powder. This is called sulfur flower. It is exactly the powder that you put in your test tube at the beginning of the experiment.