N-(Phosphonomethyl)iminodiacetic acid hydrate is the hydrated form of N-(phosphonomethyl)iminodiacetic acid (PMIDA; H4pmida). The solubility of PMIDA in various solvents and solvent mixtures has been studied. It is the starting material for the synthesis of N-(phosphonomethyl)iminodiacetate (pmida4-), a multidentate organic ligand. PMIDA undergoes molecular oxygen oxidation in the presence of metal salts to form N-(phosphonomethyl)glycine, also known as glyphosate. H4pmida forms the structural unit of various three-dimensional inorganic-organic hybrid compounds.