Chemistry of copper (I) chloride

In this experiment, some CuCl, white solid, is dissolved in conc. HCl (30%). This results in formation of a yellow/brown solution, which very quickly becomes dark brown when left in contact with air. The copper (I) chloride dissolves in HCl, forming colorless CuCl2(-). Part of this is oxidized by oxygen from air, forming copper (II), which forms a very dark brown complex with the copper (I), present in the solution. A colorless copper (I) solution can only be maintained under complete exclusion of air, as shown in http://www.woelen.nl/chem/exp0005/exp0005.htm.

The first picture shows some solid CuCl in a small amount of water. It hardly dissolves. On the glass, however, the liquid becomes brown, apparently some of this dissolves and is oxidized by oxygen from the air:

To this solid CuCl, some 30% HCl is added. All of the solid dissolves quickly and the liquid becomes dark brown very quickly:

To this dark brown liquid a small volume of 30% H2O2 is added. The liquid becomes green at once. The brown complex is destroyed immediately by the H2O2 and what remains is a green copper (II) complex in conc. HCl. Some excess H2O2 remains, which quickly decomposes and causes the bubbling of the liquid.

Finally, the liquid is diluted with water to more than 10 times its original volume. The liquid becomes light blue and no precipitate of crystalline CuCl is formed anymore. All copper (I) is oxidized to copper (II):