Assessment of the Quality of Organic Acids - Products of the Chemical Industry - by the Method of Acid-Base Titration with Potentiometric Equivalence Point Display

Purpose of the study. Show the possibilities of using ion-selective potentiometry to assess the compliance of the quality certificate of an organic acid, a product of the chemical industry, with the declared range and content of the main substance. On the example of oxalic and benzoic acids, demonstrate the possibility of determining the equivalence point using a glass electrode as an indicator. Develop a methodology for assessing the compliance of the declared range of organic acids with the gross formula in the quality certificate by comparing the experimentally determined molecular weight with the calculated one.

Methods. The technique of potentiometric acid-base titration was applied with the construction of titration curves, determination of the potential jump and the equivalence point. The possibilities of the method are demonstrated on the example of the identification of oxalic and benzoic acids. It has been shown that the method of potentiometric acidbase titration with the construction of titration curves, the determination of the potential jump and the equivalence point can be used to determine the molecular weight of poorly soluble organic acids in water.

Results. On the example of experimental curves of potentiometric titration of oxalic and slightly water-soluble benzoic acid, the possibility of determining the equivalence point from the potential jump is shown. Based on the law of equality of the equivalents of the reactants, formulas were obtained for calculating the molecular weight of an identified organic acid and the content of the main substance. A technique has been developed for assessing the compliance of an organic acid with a quality certificate using acid-base titration with potentiometric indication of the equivalence point by the response of a glass electrode. The technique is applicable to assess the quality of both soluble and poorly soluble organic acids in water.

Conclusion. Ion-selective potentiometry using a glass electrode as an indicator can be used to determine the molecular weight and content of the main substance of weak and water-soluble organic acids, chemical industry products, in order to assess their compliance with the quality certificate.

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