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Re: Aquatic Plants Digest V3 #322

On Sat, 13 Jun 1998, Bob Dixon wrote:


My complaints about the term "carbonate hardness" has been aired here 
repeatedly, so I won't do it again.   I will add that there is 
a water quality measure called "acidity" that measures the 
ability of water to resist being made alkaline.  It is the 
reverse of alkalinity; its probably what you are measuring if you 
use a CO2 test kit.

> 	Non-carbonate hardness is the measure of certain positive metallic ions, such
> as calcium and magnesium, which have an ionic valence of +2.  Wardley's kit
> for this is labeled as simply hardness, and in the instructions calls non-
> carbonate hardness "total hardness", which is kind of misleading.  It is also
> measured in ppm or degrees, as indicated by "dH" or "DH" these two scales
> differ by a fraction of a part per million, but are nevertheless two different
> scales as indicated by a lower case or upper case <D>.  Wierd, huh?

If you get a water report from your water utility and it reports
noncarbonate hardness you will find that it *isn't* the same thing as 
calcium-magnesium or general hardness, and that general hardness 
*is* the same thing as total hardness.  Noncarbonate hardness is 
the amount of the general hardness that is not balanced by carbonates in 
solution.  It's calculated as alkalinity minus general hardness, or 0, 
whichever is largest.  Noncarbonate hardness is meaningless for aquarium 

Roger Miller