Analytical aspects of some organic acids

Summary A direct complexometric titration of iron(III) with EDTA using o- and p-cresotic acids indicators is given. The colour change at the end point is from blue-violet to light yellow or colourless at low concentrations of iron(III)]. The optimum range of pH and temperature for carrying out the titrations is 1.99 to 4.2 and 35° to 55°C and 1.42 to 4.4 and 30° to 60° C, respectively. Iron(III) may easily and accurately be estimated in macro- and micro-gram quantities with the help of these metal indicators. Be, Mg, Ca, Sr, Ba, Cd, UO₂ and Mn are without any interference in the estimation. Back titration procedures for determination of zirconium and thorium with iron(III) and o- and p-cresotic acids are carried out.Part V: See Z. analyt. Chem. 173, 196 (1960).