[" Q.31.When a mixture of ammonium chloride and potassium dichromate are heated,a stable "],[" colourless gas (A) was evolved which did not support combustion but magnesium continued "],[" to burn in it.The gas reacted with calcium carbide in an electric furnace forming a solid "],[" (B).The compound (B) was slowly hydrolysed by water forming an insoluble substance (C) "],[" and the solution of substance (D) which turn Nessler's reagent brown.Identify A to D and "],[" write the reactions involve in it."]