Cietība:
Equivalent Concentration:

The equivalent concentration, symbol ceq, is defined as the amount of substance of a dissolved substance divided by the volume of the solvent (here: water), multiplied with the valency, symbol z, of the diluted substance. According to SI conventions, the unit of the equivalent concentration is mol/L ⋅ 1/z. However, in water chemistry, the obsolete – but more convenient in writing – unit meq/L is still being commonly used (in Germany also: mval/L, in Russia: мг-экв/л or mg-eq/L); in case of high concentrations of the dissolved substances (e.g. concentrated acids or bases) also eq/L.
No http://www.ewt-wasser.de/en/knowledge/concentration-quantities-unit-conversions.html
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