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KH and the Chart

Bob Dixon wrote:  " It seems to me, and I'm not a chemist, that phosphate
alkalinity should be counted in the mix here as KH.  The charts allow you to
figure in for alkalinity.  You need to do this, because alkalinity and
acidity are directly related within a given body of water."

This is incorrect.  The chart and the underlying relationship of KH/pH/CO2
concern only carbonate hardness and not other non-carbonate constituents of
alkalinity.   Our hobby kits only measure total alkalinity, but this does
not present problems if we use carbonate buffers and don't have significant
amounts of other alkalinity constituents.  I gather from Roger's note that
low levels of PO4 (say, 1 ppm or less) are not going to have any great
affect on total alkalinity and so the chart and our hobby KH kits will work
okay for our purposes.

Regards, Steve Dixon (no relation to Bob) in cold San Francisco