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**To**:**Aquatic-Plants at actwin_com****Subject**:**Re: equivalents****From**:**Greg Morin <greg at seachem_com>**- Date: Fri, 2 Feb 2001 15:24:34 -0500
- In-Reply-To: <200102012048.PAA15744 at actwin_com>
- References: <200102012048.PAA15744 at actwin_com>

Just a follow up note here as it has been pointed out that my discussion of equivalents neglected to mention that when we are discussing cations like calcium and magnesium the convention is to take into account the charge number when discussing concentration of these ions. Calcium has a +2 charge so 1 equivalent of calcium ions is the same as 2 equivalents of positive charge. By convention hardness is discussed in terms of the amount of positive charge contributed by both magnesium and calcium. Magnesium contributes 1 positive charge and calcium 2 for each individual ion of the respective elements. So by convention the hardness figures also take into account the charge contribution. So in my example in the first post, 40 mg/L of calcium is equal to 1 meq/L of calcium ions, but equal to 2 meq/L of positive charge/general hardness. -Greg Morin -- Gregory Morin, Ph.D. ~~~~~~~Research Director~~~~~~~~~~~~~~ Seachem Laboratories, Inc. www.seachem.com 888-SEACHEM ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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