AbstractThe esterification of ethylenediaminetetraacetic acid (EDTA) in a hot acidic medium gives rise to impure products. The impurities have been identified and shown to be esters of various acids: nitrilotriacetic acid; iminodiacetic acid; piperazine‐1,4‐diacetic acid; N‐methylethylenediaminetriacetic acid; N,N‐ and N,N′‐dimethylethylenediaminediacetic acids and 2‐ketopiperazine‐1,4‐diacetic acid. The reactions for the formation of these impurities are discussed and a method for the preparation of pure esters of EDTA is described. Details of some crystalline derivatives, 1H‐n.m.r. and infrared spectra of a series of esters of EDTA are presented. The determination of the molecular weights of the esters by saponification is discussed.