Characterization of a new efflorescence salt on calcareous historic objects stored in wood cabinets: Ca_2(CH_3COO)(HCOO)(NO_3)_2·4H_2O

摘要

White efflorescence crystals grown on the surfaces of a bronze bowl, classical ceramic and ancient wine jugs were investigated. X-ray powder diffraction (XRPD) revealed that in each case an identical, hitherto unknown phase was formed. The crystal structure was solved from high resolution XRPD measurements and revealed a phase composition of Ca-2(CH3COO)(HCOO)(NO3)(2)center dot 4H(2)O, which is in accordance with the complementary analysis. The overall structural motif of Ca-2(CH3COO)(HCOO)(NO3)(2)center dot 4H(2)O, one dimensional calcium carboxylate zig zag chains in which acetate and formate ions are arranged in an alternating fashion, is closely related to other naturally occurring or artificial efflorescence salts like thecotrichite or calclacite.