Re: Buffering capacity

[Doug Brown <debrown@kodak.com>]

Buffering capacity is universally measured in ppm (mg/L) of calcium
carbonate - CaCO3."KH" (or "dH" - same thing different units) and
"buffering capacity" are the same thing. There have been various water and
soil tests developed to measure this parameter. You need to know this value
to help understand your water chemistry. KH and pH are directly related.
That is, changing one will directly change the other, at least a little.
Although the units are expressed as a concentration of CaCO3, the tests
really measure overall buffering capacity wherever the buffering comes from.

General hardness, or GH (or dG) is a measure of the concentration of
calcium and magnesium in water. Depending on the actual test other ions
contribute to this measurement. It is somewhat a measure of ionic strength
(rather than buffering capacity) which can be related to conductivity for
example, so you can see that you'd want to know this value for replicating
an aquatic habitat also. It is not directly related to pH so that you can
change pH without changing GH, for example.

It is confusing that both KH (carbonate hardness) and GH (general hardness)
are sometimes reported as simply "ppm". They are not measured in the same
units, so it is quite possible for KH to be higher than GH.

Hope that clears things up.

>I wrote:
>
>><< >I noticed that Mardel's product line referred to as "Waters of the World"
>>>makes reference to buffering capacity being measured in parts per million.
>>>This strikes me as odd, but I guess that I don't really know of any other
>way
>>>to measure it except to say it is stable, fairly stable, highly stable, etc.
>>>(Certainly not very informative or scientific).
>>>
>>>Okay, so does anyone know parts of *what* per million?
> >
>
>Steve answered:
>
>> Two assumptions.  One is that buffering capacity is equal to carbonate
>> hardness.  Two is that all carbonate hardness is from calcium carbonate.
>> The conversion is one dKH is equivalent to approximately 18 ppm CaCO3.
> >>
>
>Sounds okay, but the side of the box says that South American water is ideally
>60 ppm General hardness and 120-180 ppm Buffering capacity.  Your explanation
>is inconsitant with the box info.  Any other ideas?
>
>Bob

- -Doug Brown
debrown@kodak.com