hard water

https://doi.org/10.1351/goldbook.14730
Water that contains mineral salts of divalent cations, commonly calcium and magnesium and sometimes iron(II) (ferrous) ions, principally as hydrogencarbonates, chlorides, and sulfates.
Note: Hardness caused by calcium hydrogencarbonate is known as temporary, because boiling converts the hydrogencarbonate to calcium carbonate (\(\ce{CaCO3}\)), which has a very low solubility; hardness from the other salts is called permanent.
Source:
PAC, 2009, 81, 829. (Glossary of terms used in ecotoxicology (IUPAC Recommendations 2009)) on page 893 [Terms] [Paper]
Citation: 'hard water' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.14730 RIS BibTex EndNote
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