hardness


hardness
water with a high mineral content, the name deriving from the fact that it is hard to develop a lather for cleaning. The concentration of calcium and magnesium ions in water is expressed as p.p.m. or mg/l of calcium carbonate equivalents. Soft water is 0-17, slightly hard 18-60, moderately hard 61-120, hard 121-180 and very hard 181+ p.p.m. or mg/l (and other sources give soft as 0-20, moderately soft as 20-40, slightly hard as 40-60, moderately hard as 60-80, hard as 80-120 and very hard as >120. Sometimes grains per gallon are used where 1 gpg equals 17.12 mg calcium carbonate/l. Note that different countries use or used different measures: 1 English (Clark) degree or ºE is 14.28 p.p.m. calcium carbonate, 1 American degree is 17.1 p.p.m. calcium carbonate (elsewhere as 1 p.p.m.) and 1 French degree (fh) is 10.0 p.p.m. calcium carbonate. However 1 German degree (dh or dH) is 17.9 p.p.m. calcium oxide (and elsewhere as 1 p.p.t.). Confusingly the German dh is used generally for degrees of hardness

Dictionary of ichthyology. 2009.

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  • Hardness — Hard ness, n. [AS. heardness.] 1. The quality or state of being hard, literally or figuratively. [1913 Webster] The habit of authority also had given his manners some peremptory hardness. Sir W. Scott. [1913 Webster] 2. (Min.) The cohesion of the …   The Collaborative International Dictionary of English

  • Hardness — Hardness. См. Твердость. (Источник: «Металлы и сплавы. Справочник.» Под редакцией Ю.П. Солнцева; НПО Профессионал , НПО Мир и семья ; Санкт Петербург, 2003 г.) …   Словарь металлургических терминов

  • hardness — index brutality, congealment Burton s Legal Thesaurus. William C. Burton. 2006 …   Law dictionary

  • hardness — (n.) O.E. heardnysse; see HARD (Cf. hard) + NESS (Cf. ness). Meaning difficulty of action or accomplishment is late 14c …   Etymology dictionary

  • Hardness — A finishing term that implies the cloth has a hard, papery handle such as required with shirtings for China, North Africa and elsewhere. These fabrics are heavily filled and undergo heavy pressure when fairly dry; the face of the cloth may be… …   Dictionary of the English textile terms

  • hardness — [härd′nis] n. 1. the state or quality of being hard (in various senses) 2. the relative capacity of a substance for scratching another or for being scratched or indented by another …   English World dictionary

  • Hardness — This article is about mechanical properties of materials. For other uses, see Hard. Hardness is the measure of how resistant solid matter is to various kinds of permanent shape change when a force is applied. Macroscopic hardness is generally… …   Wikipedia

  • hardness — /hahrd nis/, n. 1. the state or quality of being hard: the hardness of ice. 2. a relative degree or extent of this quality: wood of a desirable hardness. 3. that quality in water that is imparted by the presence of dissolved salts, esp. calcium… …   Universalium

  • Hardness — (Roget s Thesaurus) < N PARAG:Hardness >N GRP: N 1 Sgm: N 1 hardness hardness &c. >Adj. Sgm: N 1 rigidity rigidity Sgm: N 1 renitence renitence renitency Sgm: N 1 inflexibility inflexibility temper callosity …   English dictionary for students

  • hardness —    a measure of the hardness of a metal or mineral. Hardness is a property easy to appreciate but difficult to quantify and measure.    The Mohs hardness scale is used in geology to give a rough estimate of hardness by testing which minerals are… …   Dictionary of units of measurement

  • hardness — The toughness of the surface of a metal. See brinell hardness indentation hardness rockwell hardness shore hardness …   Dictionary of automotive terms


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