The process of heating coal in the absence of air is called the destructive distillation of coal. Coal contains a number of elements such as carbon, hydrogen, oxygen, nitrogen, and sulfur.
The tube is kept horizontally and another tube (water containing ) is fixed vertically.
Start heating wood pieces first gently and then strongly.
Observation:
You will observe that volatile substances leave the wood on heating and get condensed in another tube containing water.
These volatile substances form a deep black liquid, which settles at the bottom of the tube.
This deep black liquid is called wood tar and the gas which is escaping out from the side tube is called wood gas.
When heating is stopped and the boiling tube is cooled a black residue is left in the boiling tube.
