摘要：A titration can be done with different purposes in mind. It may be performed to determine the concentration of one or several components in a sample. Obtaining a correct value for the equivalence volume is the key question in this case. A titration may also be carried out to determine a physicochemical parameter. On this respect, potentiometric titration is, in numerous situations, the method of choice for measuring acidity constants in chemistry and biochemistry. By using the reverse function of pH=pH(V) titration curves for strong acid with a strong base at varying concentrations, as well as titration curves for monoprotic acids titrated with strong base, at the same concentration, but varying pKa from 1 to 13, may be simulated. On the basis of these curves, a study of the Gran II method is carried out in this work to outline its advantages and limitations. Gran II linearization method is one of the most cited scientific papers (over 2500 cites) and has been applied in a variety of fields. By suitable modification in the data analysis Gran plot methodology may be extended as suggested by Schwartz. The linearization method devised by Schwartz is a powerful tool to determine titrations end point and (simultaneously) acidity constants. Gran and (mainly) Schwartz methods are superior to the differential methods, which fail to give a good sharp point with very weak acids (pKa 9-10.2). In this paper some applications are outlined such as the evaluation of the autoprotolysis constant of water, and the simultaneous determination of equivalence point and acidity constant in potentiometric titrations. Several bibliographic and experimental systems (hydrochloric acid, perchloric acid, β-alanine, acetic acid, ammonium nitrate and boric acid, titrated with an alkaline solution) are studied to acquire a prior knowledge of how experimental data should be treated to fit the purpose intended.
关键词：Potentiometric titration; Gran method; Schwartz method
