The chemicals listed in this section include those found as impurities in water and also those used as treaments. The chemical formulas, ion forms, and molecular and equivalent weights are given for each substance. Abbreviations and symbols are used extensively to simplify water analysis reports and calculations. This section explains the meanings of some common symbols and what they represent in water analyses. Very often the units used in water chemistry need to be converted back and forth for practical application. For example, parts permillion may be converted to grams per 1000 litres and vice versa. The conversion factors in this section simplify this type of calculation.