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Re: Units for CEC

> From: Steve Pushak <teban at powersonic_bc.ca>
> Subject: Units for CEC
> Does anyone know if these units for CEC are equivalent? 
>          cmol/Kg (sic)   ~   meq/100 grams 
	I had always wondered what the units were when people quoted CEC's.
This gives me a clue at last!

	The two may be the same, depending on exactly how one defines
"centimole".  "meq/100 grammes" is unambiguous.  It means that 100 grams
of the material can hold 1 thousandth of a mole of an ion with a charge of
one, or half a thousandth of a mole of an ion with a charge of two, and
so on.  "Centimole" would usually refer to the amount of an ion (i.e. the
number of them) with no regard to the charge (if any, it could be for a
neutral species as well).  If the ion in question has a charge of 1, then
1 centimole of the stuff will have 1 centiequivalent of charge, and the two
units will be the same, there being 10 milliequivalents in 1 centiequivalent.
If the ion has a charge that is _not_ one, then the two units will differ
by a factor that is the ionic charge.  I suspect, though, that no regard
is being paid to charge, and that the first unit is being used sloppily,
and the two are being used interchangeably.

Paul Sears        Ottawa, Canada