Solid–Liquid Reaction Synthesis of High-Purity Potassium Hexathionate and Its Antibacterial Properties

Hexathionate, an intermediate in the oxidation process of inorganic sulfur compounds, plays important roles in different fields of chemistry, chemical technology, and biology. To achieve innovative results in different fields related to polythionates, the use of hexathionate is crucial, however, it is not yet commercially available. Herein, we report a simple and convenient method to prepare high-purity potassium hexathionate. Hexathionic acid was easily synthesised through a solid–liquid reaction between sodium thiosulfate (solid) and disulfur dichloride. The potassium salt crude product was obtained by neutralising hexathionate acid with potassium hydroxide, and was purified successively using 0.1 M sulfuric acid and 0.5 M hydrochloric acid. A high product purity of 99.8 % (titrimetric analysis, 98.81 %) was obtained. The antibacterial activities of potassium hexathionate against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Pseudomonas aeruginosa (P. aeruginosa) were determined by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) analyses and the cup diffusion method. Potassium hexathionate displayed more effective antibacterial activities against P. aeruginosa than S. aureus. The MICs against P. aeruginosa and S. aureus were 1.95 and 125 µg mL–1, respectively. The corresponding MBC value against P. aeruginosa was 1000 µg mL–1. Furthermore, the duration of the antimicrobial activity, determined by the cup diffusion, shows the potential of potassium hexathionate as a sustained antibacterial candidate. However, there is no bactericidal activity against S. aureus in the concentration range tested.