C 2673 (OTTO) Copper(II) chloride, dihydrate, 99.999% Cas 10125-13-0 - used as a catalyst for efficiently cleaving t-butyldimethylsilyl (TBDMS). C 2673 (OTTO) Copper(II) chloride, dihydrate, 99.999% Cas 10125-13-0 - used as a synthetic catalyst, a pyrotechnic coloring agent .