Ok, light reading, we want to address this statement, I presume -
"2. The pH of highly purified water is not accurately measured by test kits, or by pH meters. There are several different reasons for this, including the fact that highly purified water has very little buffering capacity, so its pH is easily changed. Even the acidity or basicity of a pH test kit’s indicator dye is enough to alter pure water’s measured pH. As for pH meters, the probes themselves do not function well in the very low ionic strength of pure freshwater, and trace impurities on them can swing the pH around quite a bit. "
What Randy is saying here is that measuring the H concentration is difficult, not because salts (buffers) are there or not, but due to lack of buffering capacity within highly pure water. With this lack of buffering, the solution is highly variable in pH due to it's environment. CO2 contributes carbonic acid to the solution altering it's pH (lowering it). Water with more buffering capacity is more resistant to these environmental changes. Which is why in my example above I say to off gas CO2 before measuring. This will give an accurate enough measure of the sample.
What Randy is NOT saying here is that pH measures salts. Also keep in mind that moving from pH of 6.9 to 6.7 is a big number mathematically, hence "quite a bit" . But for our purposes, it's minimal.
I think you've just read more into this than you needed to, and your initial claim re: measuring salts in inaccurate. pH is Latin for "weight of Hydrogen" and as described, measures Hydrogen.
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Brad
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