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Hardness in ppm

>From: RDotta7777 at aol_com

>It seems that the buffering capacity is the issue.  The water measures a
>Carbonate hardness of 40ppm with the LeMotte test kit which I equated to a
>= 5.06.

I am guessing that dCH means dGH or degrees general hardness. This means
1dH=7.9ppm.  I think you meant ppm of CaCO3 and you left off a number! 

I have only seen hardness defined in terms of calcium carbonate
concentrations (1dGH and 1dKH = 17.9ppm CaCO3).  So you mean 17.9, not 7.9!
[CaO or Ca have also been used for GH, but these have different conversions
from their ppm.]

If LaMotte measures 40ppm of CaCO3, I believe you have 40/17.9=2.2dH (both
KH and GH). 

This is a good example why degrees of hardness is not a desireable way for
people to compare hardness values, unless we are all using the same
conversion factors. 

Also, we all have to remember that when hardness is expressed in ppm, we
MUST KNOW if we are talking about ppm of calcium carbonate or calcium oxide
or calcium or calcium+magnesium or ????

Degrees hardness would be an OK way to describe hardness if all the
assumptions were adequately presented in one referenceable place and we
were SURE that the conversions were all done the same way! Hopefully Tetra,
Dupla and LaMOtte are using the same formulas <g>

When a test measures total hardness and separately presents measurements of
calcium and magnesium, it seems that the units for hardess are not presents
as CaCO3 or CaO. If it is, does anyone know what it means to present the
magnesium compound concentration in terms of equivalent Calcium or Calcium