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measures: Roger, Greg, Klaus

now i'm starting to get a bit confused about this as well. let me just throw in my two cents and see what people think.  greg morin's explaination of the meq/L sounds more to me like the definition of a mole/liter, or molar (M), or really to be dimensionally correct a millimole/L or mM. the concept of an equivalent does not just take into account the number of something (which is what is accomplished by the mole) - it is specifically useful only when dealing with charged species.  As Roger miller said it is a measurement of the molar concentration of ionic charge. it normalizes not only for weight but for the charge of a species. so, 40g ca  and 24g mg  and 23g Na are all one mole of each respective species, but all are not equivalent because Ca and Mg have twice the charge of Na.  so 23g of Na is like 1 mole of positive charge, or one eq, while 40g Ca is 2 moles positive charge or 2 eq.  the thing i don't remember is whether there's some significant relationship here between !
avogadro's number Faraday's cons

tant or something (mev and what have you).