Determination of bicarbonate in fresh and drinking waters by potentiometry. A simulated lab experiment.

Abstract

In this exercise, the concentration of bicarbonate (hydrogen carbonate) in a sample of fresh (or drinking) water is determined by potentiometry. The aliquot for analysis is 50 milliliters and the titrant concentration ( HCl ) is determined by the amount of bicarbonate in the sample. In this simulated titration, this amount is in the range of 20-300 milligrams per liter . A preliminary evaluation with colorimetric indicator ( methyl orange ) allows to quickly find the equivalence point in milliliters. The purpose of this operation is to make the potentiometric titration faster allowing the change in the parameters of the analysis ( sample aliquot or concentration of HCl) if necessary. With the obtained data, the potentiometric titration curve is drawn using a spreadsheet and the equivalence point is obtained from the graph of the first derivative. The analysis is performed in quintuplicate and the result is given as the mean value of the determinations. The data are randomly generated . The laboratory experiment ends with two self-evaluation exercises.