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Re: Aquatic Plants Digest V4 #817



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>
> Date: Thu, 1 Feb 2001 13:11:52 -0800 (PST)
> From: Adele and Davis Gailitis <adele_davis at yahoo_com>
> Subject: Measures
>
> Ok so call me a little slow BUT........what the !$@!
> is meq/l ???????????? this has been used extensivly in
> the thread: "Equilibrium, Ca and Mg levels" is this
> suposed to be mg/l ??????
>
Hello Davis,
up to somes days I was confused too. Now it's clear. First, meq/l is equal
to mval/l.
Let me explain it by an example:
My water has a content of 91 mg/l Calzium (Ca++) and 2,5 mg/l Natrium (Na+),
of course, other Ions too. The atomic weight of Ca is 40,1 g and of Na is 23
g. Ca, as an ion, has two positive charges, therefore Ca++. Na, as an ion,
has only one positive charge, therefore Na+. If you devide the atomic weight
by the charge, you get the dimension "meq". In my case for Ca++ it means,
40,1 g / 2 = 20,05 g = 1 meq and for Na+ it means 23 g / 1 = 23 g = 1 meq.
Back to the "mg/l". For Ca++ : If 20,05 g (equal to 20.050 mg) are equal to
1 meq, then 91 mg/l Ca++ are equal to 4,5 mmeq/l. For Na+ : If 23 g (23.000
mg) are equal to 1 meq, then 2,5 mg/l Na+ are equal to 0,11 mmeq/l.
The "meq resp. mval" was created, because it was found, that chemical
connections will function only in the relationship of there "ü─quivalenzen".
(Sorry for incorrect language, but english is not my motherlanguage).
The calculation with meq is importent when designing a
KATI/ANI-ion-exchanger to get low hardness in the water. My tapewater has in
_summery_ a total content of kations of 6,6 meq. If one liter of resin has a
capacity of about 1250 meq/l (usible), does it mean, you get 1250 meq/l /
6,6 meq= 189 l water, then you have to regenerate the resin. And now it is
to understand, that an exchanger can exchange the double quantity of
one-charge-kations than of two-charge-kations. Mostly, the capacity of
ion-exchangers are calculated by "Hardness*Liter". That means, does an
exchanger has a capacity of 9000 HL (_H_ardness*_L_iter) and the tape water
has total hardness about 18 ü░dH, you get 9000/18=500 liter of water before
regeneration. This is valid **only**, if the tapewater consists of
one-charge-ions, f.e. Natrium, Kalium a.s.o. In all other cases, that means
practical always, you have to design an exchanger by the meq-method.

I hope it was helpful to you, best regards, Klaus.







> Dazed and Confused
> Davis:)
>
>
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