Preparation of copper acetylide
100 grams of copper sulfate pentahydrate and 50 grams of sodium chloride are dissolved in 300 ml of water. The solution is filtered to remove all undissolved residues. The filtered solution is gently heated and sulfur dioxide is passed through this solution. After a short time, the white copper(I) chloride starts to appear. The mixture is allowed to settle, filtered and washed with distilled water. The freshly prepared copper(I) chloride is dissolved in 400 ml concentrated (25%) aqueous ammonia solution and left to stand for 12 hours. Then to the prepared solution of copper(I) chloride in aqueous ammonia gaseous acetylene is introduced. Copper acetylide starts to form and the acetylene gas is passed until the reaction is complete and all copper is reacted. The reaction product is washed with plenty of water and dried at room temperature. Copper acetylide explodes on impact, also in contact with nitric acid, sulfuric acid, potassium permanganate solution, bromine, chloride.
Handbuch der präparativen chemie, by Ludwig Vanilo, 1922, 32.