Thermal analysis of binary and ternary systems of salicylic acid, sodium salicylate and sodium hydrogen carbonate

Abstract

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.

Amorphism and Thermal Decomposition of Salicylsalicylic Acid—A Cautionary Tale

“…The starting point for our study was a preliminary investigation in the solid state using 13 C CP/MAS spectroscopy to look at what was supposed to be a sample of amorphous salsalate produced by heating a sample of the commercial material to its melting point (or slightly above) and then rapidly cooling it to room temperature. Using this method, it was possible to tentatively assign signals due to the linear trimer and linear tetramer of salicyclic acid, with a significant number of lower intensity peaks unassigned, which were presumed to be due to longer oligomers.…”

“…The cyclic nature of such a molecule and its aromaticity may be reasonably expected to facilitate alkali cation adduction. [11] Cyclic species have been prepared previously [12] and observed as thermal decomposition products of both salicylic acid and acetylsalicylic acid (aspirin) [13,14] but only at much higher temperatures (> 300 o C). We therefore decided to investigate more closely the peaks that appeared as possible cyclic species using ion mobility measurements.…”

Thermogravimetric studies of binary and ternary systems containing salicylic acid, sodium salicylate, sodium carbonate and sodium hydrogen carbonate. Part II

“…Disodium salicylate sesquihydrate was obtained by drying in air disodium salicylate obtained as reported previously [2].…”

“…Preliminary tests revealed the possibility of application of thermogravimetry to analyze binary systems whose components interact, and to check declared compositions of mixtures containing salicylic acid [2]. Ternary systems can be analyzed via reactions occurring at elevated temperatures, which eliminate one of the components, thereby leaving binary systems.…”

“…Thermal decomposition of a system containing disodium salicylate sesquihydrate and sodium carbonate (system I). Loss in weight as a function of temperature (1) and composition (2). The decomposition of the sesquihydrate is described by Eqs (8), (10) and (11) Fig.…”