Basic Copper Chloride(WSDTY) trihydroxide Cu2(OH)3Cl is a green crystalline solid. It decomposes above 220 °C with elimination of hydrochloric acid to oxides of copper. It is largely stable in neutral media, but decomposes by warming in alkaline media, yielding oxides. It is virtually insoluble in water and organic solvents, soluble in mineral acids yielding the corresponding copper salts (eq. 1), soluble in ammonia, amine and EDTA solutions under complex formation. It can easily be converted to copper hydroxide by reacting with sodium hydroxide (eq. 2). Its pH in water is 6.9 measured by EPA method SW846-9045.
Cu2(OH)3Cl + 3 HCl → 2 CuCl2 + 3 H2O (eq.1)
Cu2(OH)3Cl + NaOH → 2Cu(OH)2 + NaCl (eq.2)
Most of the published scientific literature on the properties of the compound has focused on specimens found as natural minerals or corrosion products on copper alloys, or prepared under laboratory conditions.
Hydrolysis of CuCl2:Cu2(OH)3Cl can be prepared by hydrolysis of a CuCl2 solution at pH 4 ~7. A variety of bases such as sodium carbonate, ammonium, calcium, or sodium hydroxide may be used (eq. 3).
2CuCl2 + 3 NaOH → Cu2(OH)3Cl + 3 NaCl (eq.3)
Cu2(OH)3Cl can also be prepared by the reaction of a hot CuCl2 solution with freshly precipitated CuO (eq. 4).
CuCl2 + 3 CuO + 3 H2O → 2 Cu2(OH)3Cl (eq.4)
If sufficient chloride ions are present in solution, hydrolysis of CuSO4 with alkali also produces Cu2(OH)3Cl (eq. 5).
2 CuSO4 + 3 NaOH + NaCl → Cu2(OH)3Cl + 2 Na2SO4 (eq.5)
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