Sodium chloroaurate, also known as "sodium chloroaurate(III)", has the chemical formula NaAuCl4·2H2O and a molecular weight of 397.80. It is an orange-yellow orthorhombic plate-like crystal. It is readily soluble in water, ethanol, and ether. It is stable in air but decomposes at 100°C. Preparation: It is obtained by reacting gold trichloride with sodium chloride using 5% hydrochloric acid as a solvent. Uses: It is used in photography, glass coloring, and pharmaceuticals.
Sodium chloroaurate is used as a substitute for chloroauric acid in the determination of gold content in ores. The determination of gold content in ores typically involves dissolving the gold in aqua regia to form chloroauric acid, followed by atomic absorption spectrometry or volumetric methods. However, the stability of chloroauric acid solutions is easily affected by factors such as temperature, acidity, concentration, external conditions, and container adsorption. Alkali metals can be used to generate relatively stable chloroauric acid salts to improve the stability of chloroauric acid solutions, but this method has not been practically applied. This paper proposes a method for determining gold content in ores using sodium chloroaurate as a standard solution instead of chloroauric acid. The standard solution prepared using this method showed no low reduction after 3-4 months of storage. The method involves enriching gold using an activated carbon adsorption column, dissolving it in aqua regia, and then adding a saturated sodium chloride solution to prepare a sodium chloroaurate solution. The gold content is determined using atomic absorption spectrometry on a Hitachi Z-2000 atomic absorption spectrophotometer. Experimental results show that the determination method is reliable, has small error, and good stability; the absolute sensitivity can reach 0.025 μg/g, and the determination range is 0.04～1000 μg/g, making it suitable for the determination of gold in large batches of geological mineral samples.
