Cuprous acetylide, Cu₂C₂

The Cuprous acetylide, Cu₂C₂, is formed by the action of acetylene on an ammoniacal solution of cuprous chloride, or on a suspension of cuprous oxide in water. It is a brownish-red, amorphous substance, and explosive in the dry state. Prepared by the first method, it is associated with a molecule of water, which can be removed by drying over sulphuric acid. The presence of this water has been attributed to adsorption, and another explanation assumes the compound to have the formula CH≡CCu,CuOH. Cuprous acetylide forms complex derivatives with solutions of cuprous chloride and potassium chloride in hydrochloric acid. Among the examples of those described are the colourless 2CuCl,C₂H₂ and 4CuCl,KCl,C₂H₂; the yellow 8CuCl,2KCl,C₂H₂; and the violet 2CuCl,Cu₂O,C₂H₂. Manchot found that excess of acetylene combines with cuprous chloride to form white crystals of the formula CuCl,C₂H₂. In presence of hydrochloric acid a dark-violet powder of the composition CuCl,C₂Cu₂,H₂O is precipitated. In the dry state this substance is moderately stable. Acetylene combines with excess of cuprous chloride to form white prisms of the composition 2CuCl,C₂H₂.