Hardness caused by calcium or magnesium existing in compound form with chloride, sulfate, and nitrate anions rather than with the more common carbonate or bicarbonate anions. Non-carbonate hardness will not be precipitated by boiling. Non-carbonate hardness is the excess of total hardness over total alkalinity. High concentration (e.g. as caused by evaporation) of non-carbonate hardness anions can make the water more corrosive. The term non-carbonate hardness has largely replaced the term permanent hardness, which has the same meaning.