Carbonate hardness


Carbonate hardness

Carbonate hardness is the measure of Calcium and Magnesium and other hard ions associated with carbonate (CO32-) and bicarbonate (HCO3-) ions contained in a solution, usually water. It is usually expressed either as "parts per million" (ppm or mg/L), or in "degrees" (KH - from the German "Karbonathärte"). One German degree of carbonate hardness is equivalent to about 17.8575 mg/L. Both measurements (mg/L or KH) are usually expressed "as CaCO3" – meaning the amount of hardness expressed as if calcium carbonate was the sole source of hardness. Every bicarbonate ion only counts for half as much carbonate hardness as a carbonate ion does. If a solution contained 1 liter of water and 50 mg NaHCO3 (baking soda), it would have a carbonate hardness of about 18 mg/L as CaCO3. If you had a liter of water containing 50 mg of Na2CO3, it would have a carbonate hardness of about 29 mg/L as CaCO3.

Carbonate hardness supplements non-carbonate (a.k.a "permanent") hardness where hard ions are associated with anions such as Chloride that do not precipitate out of solution when heated.

Carbonate hardness is removed from water through the process of softening. Softening can be achieved by adding lime in the form of Ca(OH)2, which reacts first with CO2 to form calcium carbonate precipitate, reacts next with multi-valent cations to remove carbonate hardness, then reacts with anions to replace the non-carbonate hardness due to multi-valent cations with non-carbonate hardness due to calcium. The process requires recarbonation through the addition of carbon-dioxide to lower the pH which is raised during the initial softening process.


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  • carbonate hardness — karbonatinis kietis statusas T sritis Standartizacija ir metrologija apibrėžtis Vandens kietis, kurį sudaro Ca arba Mg rūgštieji karbonatai. atitikmenys: angl. carbonate hardness; temporary hardness vok. Karbonathärte, f; temporäre Härte, f;… …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

  • carbonate hardness — karbonatinis kietumas statusas T sritis chemija apibrėžtis Vandens kietumas, kurį sudaro Ca arba Mg vandenilio karbonatai. atitikmenys: angl. carbonate hardness; temporary hardness rus. временная жесткость; карбонатная жесткость ryšiai: sinonimas …   Chemijos terminų aiškinamasis žodynas

  • carbonate hardness —    Hardness of water due to presence of dissolved bicarbonates of calcium and magnesium which can be removed by boiling and hence the term ‘temporary hardness.’    Synonyms: (French.) dureté temporaire; (German.) temporäre Härte, Carbonathärte;… …   Lexicon of Cave and Karst Terminology

  • non-carbonate hardness — nekarbonatinis kietis statusas T sritis Standartizacija ir metrologija apibrėžtis Vandens kietis, kurį sudaro vandenyje ištirpusios stiprių rūgščių Ca arba Mg druskos. atitikmenys: angl. non carbonate hardness; noncarbonate hardness; temporary… …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

  • non-carbonate hardness — nekarbonatinis kietumas statusas T sritis chemija apibrėžtis Vandens kietumas, kurį sudaro vandenyje ištirpusios stiprių rūgščių Ca ir Mg druskos. atitikmenys: angl. non carbonate hardness; noncarbonate hardness; permanent hardness rus.… …   Chemijos terminų aiškinamasis žodynas

  • 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 — 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… …   Dictionary of ichthyology

  • hardness —    1. Property of water that prevents lathering because of the presence of cations, mainly calcium and magnesium, which form insoluble soaps [10].    2. The sum of calcium and magnesium ions expressed as the equivalent amount of calcium carbonate …   Lexicon of Cave and Karst Terminology

  • noncarbonate hardness — nekarbonatinis kietis statusas T sritis Standartizacija ir metrologija apibrėžtis Vandens kietis, kurį sudaro vandenyje ištirpusios stiprių rūgščių Ca arba Mg druskos. atitikmenys: angl. non carbonate hardness; noncarbonate hardness; temporary… …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

  • temporary hardness — nekarbonatinis kietis statusas T sritis Standartizacija ir metrologija apibrėžtis Vandens kietis, kurį sudaro vandenyje ištirpusios stiprių rūgščių Ca arba Mg druskos. atitikmenys: angl. non carbonate hardness; noncarbonate hardness; temporary… …   Penkiakalbis aiškinamasis metrologijos terminų žodynas