Sodium tetrathionate dihydrate is primarily used in biochemical research, particularly in the study of enzymatic reactions and redox processes. It serves as a substrate or reagent in assays to investigate the activity of enzymes like thiosulfate sulfurtransferase, which plays a role in sulfur metabolism. Additionally, it is employed in the preparation of buffer solutions for specific experimental conditions, aiding in maintaining stability during biochemical analyses. In analytical chemistry, it is utilized as a standard or reference compound in titrations and other quantitative methods to determine the concentration of other substances. Its role in these applications highlights its importance in advancing scientific understanding of metabolic pathways and chemical interactions.