Refinements of potentiometric titration: apparatus and calculations

Abstract

The method described in Chapter 2 can be scaled down, with no loss of accuracy and with a small gain in speed. It can be used for as little as one twenty- thousandth of a mole dissolved in 10 ml water (0∙005m). This effects a great economy of material. A balance weighing accurately to10µg (i.e. a good ‘five- place’ balance) is required, also a micrometer syringe to deliver 0∙5 ml of 0∙1n titrant in 0∙050-ml portions. The minimal volume of solution that can be titrated is 10 ml (in a 30-ml beaker): no smaller volume can, usually, cover the standard electrode assembly shown in Fig. 2.1. We have found this method very useful for routine determinations on new substances and have used it regularly since 1954. For more concentrated solutions, or for smaller fractions of a mole, a micro titration should be performed.