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

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Permanent hardness is caused by calcium sulphate which is soluble in 400 parts of water and cannot be removed by boiling.

From Project Gutenberg

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

From Project Gutenberg

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

From Project Gutenberg

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

From Project Gutenberg

Permanent hardness in water, due to the presence of gypsum or sulphate of lime in solution, may be remedied by addition of caustic soda.

From Project Gutenberg

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