S 2813 (OTTO) Syringic acid, 98% Cas no 530-57-4 - used as an inhibitor of poly(ethylene glycol) oxidation. S 2813 (OTTO) Syringic acid, 98% Cas no 530-57-4 - used for the preparation of poly(1,4-phenylene oxide). It is added as an additive in wine and vinegar.