Re: Water chemistry assistance

On Mon, 8 Jul 1996, George Booth wrote:

> > Is KH part of the GH?
> In generally accepted *hobbyist* terms, KH is the measure of HCO3- and
> CO3--; GH is the measure of Ca++ and Mg++.  KH and GH are totally
> separate. 
> However, typical hobbyist test kits seem to measure total *alkalinity*
> or acid buffering and call the results "KH".  If carbonates are the
> only buffer in your water, i.e., the only contributor to alkalinity,
> this is OK.

Some of the confusion seems to stem from the units used.  For example,
you can find GH, KH, alk, whatever, all measured in mg/l CaCO3.  So
people think that says something about limestone content in their
water, and wonder how come that substance contributes to all those
different parameters.

It doesn't help that, ummm, experts don't get it right sometimes.  I
have a friend who went to a recent fish club meeting in which the
speaker was explaining how water softeners (meaning the salt eating
gizmos which exchange Na for divalent metals) reduce buffering
capacity.  My friend gently tried to set things straight, but the
speaker was an importer of "africans" for a long time so clearly knew
more than a geologist could about aquarium buffering.

> Some test kits measure "total hardness" which is a combination of 
> KH and GH.  This type of measurement is of little value to us. 

But be aware that not every kit measuring "total hardness" does this.
The Hach total hardness kit measures just the usual GH.  They call it
total hardness because a person may also get a kit varient which
measures the calcium portion of total hardness if so desired.

> Just so I don't get flamed yet again by our chemistry professionals,
> "KH" and "degrees" are scientifically undesireable terms.  But since
> the test kit makers continue to use them, so will I.


Keith  2750umol Ca, 4115umol Mg, 2.3meq/l  Rogers