What is meant by destructive distillation of coal ?

Coal is not pure carbon. It is a mixture of a large no. of complex organic compounds. On heating strongly in the absence of air, coal gives many useful products.

In laboratory, the destructive distillation of coal is carried out as follows:

Two hard glass boiling tubes are taken. A small quantity of powdered coal is placed in one of the boiling tubes (tube A).About 20 ml of water is taken in tube B. The apparatus is set as shown. Coal powder is heated first gently and then strongly. The gaseous products formed during heating are passes through the water in tube B. Soluble substances dissolve in water. A tarry substance gets collected atomic the bottom of this tube.

The uncondensed and insoluble gas leaves from the exit tube. This gas is called coal gas. The black residue left in the boiling tube A is called coke. The dark tarry substance collected atomic the bottom of tube B is called coal tar.

The aqueous solution in tube B is called ammniacal solution. So, the products obtained from the distillation of coal are,

  • Solid: coke
  • Liquid/solution: Ammoniacal solution, Coal tar
  • Gas:Coal gas