What Units are Used in Expressing Water Analysis Results?
The most common unit is parts per million. One p.p.m. of a substance in a water sample represents one unit mass of the substance in each million unit mass of the water. For example, one p.p.m of salt (NaCl) means one kg of salt per million kg of water. There is still some die-hard use of the classic unit grains per gallon (g.p.g.) but this expected to disappear due to universal S.I. usage as will the unit equivalents per million (e.p.m). This mention is therefore made merely as a matter of record.
