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The thermal decompositions of binary and ternary systems of salicylic acid, monosodium salicylate, disodium salicylate and sodium hydrogen carbonate were studied by thermogravimetry and differential thermal analysis. The possibility was shown of analyzing systems involving components which react with each other upon heat treatment. Use can be made of results of this work to follow the course and extent of the reaction employed in the commercial method of. manufacturing sodium salicylate and to check declared compositions of salicylate mixtures.The thermal decomposition of salicylates has been studied by Pirisi and Mattu [1, 2], Yasutake and co-workers [3,4] and Radecki and co-workers [5,7]. The objective of this work was to develop a procedure for following the course and extent of the commercial process of manufacturing sodium salicylate [8] and for analyzing mixtures containing salicylic acid and its salts. Experimental MaterialsPure, sublimed salicylic acid and AnalaR grade sodium hydrogen carbonate were used.Monosodium and disodium salicylates were obtained by neutralizing an ethanolic and aqueous solution, respectively, of salicylic acid with a stoichiometric quantity of sodium hydrogen carbonate. The monosodium salt was crystallized from water. The disodium salt was additionally washed with 75 o ethanol to remove excess of salicylic acid. The identity of the salts was confirmed by results of elemental analyses performed by a flash-combustion method [9]. MethodsThermogravimetry was carried out in air using a Paulik-Paulik-Erdey (MOM, Budapest) Derivatograph [10]. Samples (200 rag) of powdered and intimately mixed component s were analyzed. Decomposition was carried out in platinum crucibles at a rate of 5 deg/min up to 500 ~ using e-A120 a as reference material.