A Student-Designed Potentiometric Titration: Quantitative Determination of Iron(II) by Caro's Acid Titration

A laboratory experiment involving the feasibility of using Caro's acid, H 2 SO 5, as a titrant in the potentiometric determination of iron (II) is presented. Specific items considered in the experiment include (i) method of endpoint detection; (ii) shelf-life stability of titrant; (iii) accuracy, relative precision and experimental uncertainty; and (iv) which common cations and/or anions (if any) interfere with the titration. Typical student results gave iron (II) concentrations within 1-2 % of the "true" values. Of the 14 cation/anion pairs suggested in the paper, only time(II) was found to interfere with the quantitative determination of iron (II) using Caro's acid titrant.