Hanna Instruments HI 903 - Titration Theory

3
TITRATION THEORY
Contents
1 GENERAL REVIEW OF TITRATION THEORY ............................................................................. 5
1.1 Introduction to Titrations .................................................................................................. 5
1.2 Uses of Titrations .............................................................................................................. 5
1.3 Advantages and Disadvantages of Titrations .................................................................... 6
2 TYPES OF TITRATION ........................................................................................................... 7
2.1 Titrations According to The Measurement Method ............................................................. 7
2.1.1 Amperometric Titrations .......................................................................................................... 7
2.1.2 Potentiometric Titrations ......................................................................................................... 7
2.1.3 Spectrophotometric Titrations .................................................................................................. 8
2.2 Titrations According to The Reaction Type ........................................................................ 9
2.2.1 Karl Fischer Titration............................................................................................................... 9
2.2.1.1 History of Karl Fischer Titrations ............................................................................................... 9
2.2.1.2 Visual Indication of Karl Fischer Titrations ................................................................................. 10
2.2.1.3 Electrometric Indication of Karl Fischer Titrations ....................................................................... 10
2.2.2 Acid - Base Titrations .............................................................................................................. 11
2.2.3 Argentometric Titrations .......................................................................................................... 12
2.2.4 Complexometric Titrations ....................................................................................................... 12
2.2.5 Ion Selective Titrations ............................................................................................................ 13
2.2.6 Non-aqueous Solvent Acid - Base Titrations............................................................................... 13
2.2.7 Precipitation Titrations ............................................................................................................ 14
2.2.8 Redox Titrations ..................................................................................................................... 14
2.3 Titrations According to The Titration Sequence ................................................................ 15
2.3.1 Back Titrations ....................................................................................................................... 15
2.3.2 Multiple End Point Titrations .................................................................................................... 15
3 INTRODUCTION TO TITRATION APPARATUS AND TYPICAL TITRATION PROCEDURE ................ 17
3.1 Manual Titration ............................................................................................................... 17
3.2 Automatic Titration .......................................................................................................... 18
4 TITRATION RESULTS .......................................................................................................... 19
4.1 Accuracy .......................................................................................................................... 19
4.2 Repeatability .................................................................................................................... 19
4.3 Sources of Error ............................................................................................................... 19
4.3.1 Sampling Errors ..................................................................................................................... 19
4.3.2 Errors with Titrant and Standard .............................................................................................. 19
4.3.2.1 Preparation Errors .................................................................................................................. 19
4.3.2.2 Dispensing Errors ................................................................................................................... 20
4.3.3 Chemical Reaction Errors .................................................................................................. 20
4.3.4 End Point Determination Errors ........................................................................................ 20
5 CALCULATIONS .................................................................................................................. 21
5.1 Equations Used in Karl Fischer Titrations ........................................................................... 21
5.1.1 Calculation of water content as % mass from samples measured by mass.................................... 21
5.1.2 Calculation of water content as % mass from samples measured by volume ................................. 21
5.1.3 Calculation of water content as % volume from samples measured by volume .............................. 21
5.1.4 Calculation of water content subtracting Background Drift Rate .................................................... 21
5.1.5 Calculation of water content in external dissolutions samples ...................................................... 22
5.1.6 Calculation of water content in external extraction samples ......................................................... 22
5.1.7 Calculation of water content in gaseous samples ....................................................................... 22
5.1.8 Calculation of Titer (water equivalent of the titrant) using sodium tartrate dihydrate containing 15.66% water
by mass................................................................................................................................. 22
5.1.9 Calculation of Titer (water equivalent of the titrant) using water standards ................................... 23
5.2 Equations Used in Titrations ............................................................................................. 23
5.2.1 Sample Calculation ................................................................................................................. 23
5.2.2 Standardize Titrant ................................................................................................................. 23
5.2.3 Blank Titration ........................................................................................................................ 24
5.2.4 Multiple End Point Titration ...................................................................................................... 24
5.2.5 Back Titration ......................................................................................................................... 25
6 GLOSSARY ........................................................................................................................ 26