The Occurrence of Copper 1 Arsenide in Archaeological Artifacts

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copper 1 arsenide, also known as tricopper arsenate and cupric arsenate, is a solid crystalline copper salt. It is soluble in water and aqueous ammonium and dilute acids and is used as a pesticide, herbicide, and fungicide.

Its chemical formula is C3(AsO4)2*4H2O, and it is a blue or bluish-green powder. The CAS number is 7778-41-8 or 10103-61-4.

Cu3As is the expected intermetallic phase in arsenical copper alloys. It is a hexagonal crystallographic phase, stable only above 340″ C. In the present study, we investigated the occurrence of this phase in four prehistoric archaeological arsenical copper artifacts using micro-energy dispersive X-ray fluorescence spectrometry (MDXRF) and synchrotron radiation X-ray diffraction.

The occurrence of this phase in our archaeological artifacts indicates that it was precipitated during long-term aging at room temperature. This is important for understanding the original properties of the artifacts, as well as their possible degradation mechanisms.

Our results suggest that the trigonal a domeykite -type Cu3As in our artifacts has a composition a t least a t 700″ C and is in equilibrium with metallic arsenic a t 550″ C. In addition, we found a new phase in some alloys quenched from 700″ C or annealed at 280″ C that lacked the peritectoid decolnposition of the Cu3As E phase.

The homogeneity limit of the a domeykite-type Cu3As phase is very narrow under normal conditions and does not depend on the total alloy composition, but may be slightly altered under pressure. This may explain the lack of a uniphase specimen inay in our experiments.