Ethyne gas is prepared by the reaction of water with calcium carbide (CaC2). Ethyne gas is a colourless gas.

Main Chemicals required

  • Calcium Carbide (CaC2) [also known as calcium dicarbide] – A white/gray solid
  • Acidified copper (II) sulfate solution
  • Water


  1. Set up the apparatus as shown in the diagram.
  2. Place few pieces of calcium carbide in a Büchner flash.
  3. Add water from the dropping funnel, few drops at a time.
  4. Collect the gas produced in the test tube.
  5. Discard the first test tube as it a mixture of air and ethyne.


The ethyne gas burns with a luminous smoky flame with soot as a result of unburnt carbons.

Addition of Bromine Test

  • Bromine water turns from yellow/red colour to colourless.
  • The decolorisation of bromine is the standart test for unsaturation in a compound.

Addition of Acidified Potassium Permanganate (KMnO4) Test

  • Purple colour to colourless.
  • This is also used to test for presence of a C ≡ C triple bond (unsaturation).

Video Demonstration