Copper(I) chloride is white when pure. It does not dissolve in water. It is green when in air because of conversion to copper(II) chloride. It can react with Lewis bases, a group of chemicals. It dissolves in hydrochloric acid easily. It dissolves in solutions that have ammonia in them. It absorbs carbon monoxide. It easily disproportionates into copper and copper(II) chloride. It reacts with ammonia and acetylene to make copper(I) acetylide, a reddish explosive.
It can be made by reduction of copper(II) chloride. It was made at first by reacting copper with mercury(II) chloride. It can be made by heating copper(II) chloride very hot. Some chlorine is released, and copper(I) chloride is left behind.