What is the relationship between total hardness and total alkalinity?
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Total hardness category ①: temporary hardness. The substances that precipitate when water is boiled are mainly calcium and magnesium bicarbonates. ②Permanent hardness. The substances that do not precipitate after water is boiled, such as chlorides, sulfates, and nitrates of calcium and magnesium. ③Negative hardness. When the total alkalinity exceeds the total hardness, the excess amount represents hardness from substances such as sodium carbonate and potassium carbonate. Relationship ①: When total hardness > total alkalinity: Permanent hardness = total hardness – total alkalinity; Temporary hardness = total alkalinity. SO42- + Cl- + NO3- > K+ + Na+. ②: When total hardness = total alkalinity: In this case, only temporary hardness exists. Temporary hardness = Total hardness = Total alkalinity. SO42- + Cl- + NO3- = K+ + Na+. ③ When total hardness
Total hardness is closely related to total alkalinity. When the total hardness is greater than the total alkalinity, there is permanent hardness and temporary hardness, with the temporary hardness being equal to the total alkalinity ； When the total hardness is less than the total alkalinity, negative hardness and temporary hardness exist, where the temporary hardness is equal to the total hardness. When the total hardness is equal to the total alkalinity, only temporary hardness exists, and this temporary hardness is equal to both the total hardness and the total alkalinity. This relationship can be used to verify the validity of data through the measurement results of cations and anions, but for heavily polluted water bodies, more complex analyses are required. .