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Kh, Ph, Buffering, and Baking Soda.

In order learn something about the relationship between Ph, Kh, and
buffering, I conducted the following experiment.

Using a 5-gallon bucket of water that I removed from my aquarium in the
course of a normal water change, I began adding Baking Soda in 1/4
tablespoon doses, resulting in the following results.

Dose    Ph      Kh (dH)

0           6.5      4
1           6.6      5
2           6.7      6
3           6.8      9
4           7.0      11

In doing the Ph tests, I actually have 5 test tubes, so I can lay them side
by side on white paper, and see straight progression of color from 6.5 to

So, I want to ask anyone who knows... Previous to doing this test, I had
understood that the term Ph Buffering refers to using a substance that adds
alkalinity, (the ability to absorb acids), without actually changing Ph.
But in this test, the Ph changed along with the Kh.

So, in adding baking soda, I increased both the Ph, and the Kh.  Is this
what Ph Buffering looks like?

I am following the advise of those who say, "don't start adding CO2 to your
aquarium until you understand Ph buffering and the relationship between Kh,
and Ph."

So, if I added CO2 to the water described above, would there be a
precipitous, unmanageable, Ph drop?