SYNTHESIS, STRUCTURE AND SPECTROSCOPIC PROPERTIES OF BISMUTH CITRATE COMPOUNDS .2. COMPARISON BETWEEN CRYSTAL-STRUCTURES OF SOLID BISMUTH CITRATES AND COMMERCIAL CBS, USING THERMAL AND SPECTROSCOPIC METHODS

Spectroscopic and thermal properties of colloidal bismuth subcitrate (CBS) have been studied in the solid state, using thermal analysis (both under dinitrogen and under dioxygen), infrared spectroscopy and mass spectroscopy. The properties have been compared with previously studied (crystalline) potassium/ammonium bismuth citrate compounds, both in the solid and in aqueous solution. The thermal analysis study allows the assignments for the presence of K+, NH4+ and citrate(3-) ions. The major conclusions of this investigation are: (i) the solid product CBS most likely contains units [Bi(cit)]2, aggregated using bridging citrates into networks, separated by cations and water molecules, and similar to earlier reported crystalline Bi citrate compounds; (ii) the citrate(4-) anions universally form bridges towards two (or in same cases to even more) neighbouring Bi ions.