How can I reduce copper(II) chloride to copper(I) chloride in aqueous solution (and precipitate it out)?

Question

How can I reduce copper(II) chloride to copper(I) chloride in aqueous solution (and precipitate it out)?

Answer 1

sodium cyanide reduces Cu+2 to Cu+1

add concentrated ammonia to the Cu+2  to make the dark blue  complex [C2(NH3)4]+2

add a dilute solution of NaCN slowly until the color of the copper+2 is gone

do not add an excess of cyanide, for this will make CuI soluble.

neutralize the solution with HNO3, and CuCl should ppt, ( it is not soluble in water)