permanent hardness

British

noun

chem hardness of water that cannot be removed by boiling as it results mainly from the presence of calcium and magnesium chlorides and sulphates

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Example Sentences

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Boiling the water does not affect these salts; hence such waters are said to have permanent hardness.

From An Elementary Study of Chemistry by McPherson, William

The total hardness of water is therefore commonly made up of temporary and permanent hardness.

From Scientific American Supplement, No. 392, July 7, 1883 by Various

There are water supplies whose hardness can be corrected and there are supplies of the type known as "permanent" hardness.

From The Consumer Viewpoint by Maddocks, Mildred

What do the terms "temporary" and "permanent" hardness of water mean?

From Human Foods and Their Nutritive Value by Snyder, Harry

Calcium sulphate, or gypsum, on the other hand, imparts permanent hardness.

From Human Foods and Their Nutritive Value by Snyder, Harry

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023