Disodium phenyl phosphate hydrate is primarily used in biochemical research as a substrate for studying enzyme activity, particularly alkaline and acid phosphatases. It helps in understanding the mechanisms of enzyme-catalyzed reactions, enzyme kinetics, and their role in metabolic processes. Additionally, it finds use in the synthesis of organic compounds, acting as a precursor or intermediate in the production of pharmaceuticals and fine chemicals. Its water-soluble nature makes it suitable for use in aqueous-based systems such as enzyme assays.