The Reaction of Mono-, Di-, and Trisodium Orthophosphate in a Mixed Solution of Acetic Acid and Acetic Anhydride

Mono-, di-, or trisodium orthophosphate was heated at 100°C in an equivolume mixture of acetic acid and its anhydride. By X-ray diffractometry and paper chromatography, the products from these three sodium salts of orthophosphate were found to be sodium trimetaphosphate. At the end of the 30-hr reaction period, the purity of the trimetaphosphate was higher than 90%. The ease of formation of the trimetaphosphate ring under various conditions was shown, and the stability of the ring was discussed on the basis of the strain of the bonding angle.