" If the DI water really is DI, the PH should be exactly
7.00. Although that is almost impossible to attain. DI water starts
absorbing CO2 and the PH starts going down almost immediately unless you
shield the water. If your DI water has a high or low PH, it simply is no
longer DI water.

That is really not so at all. No RO/DI or any type of filtration gets it to exactly 7.
For all practical purposes RO/DI water has a pH range from 6.2-7.8 and that is
Ultra -Pure @ 18 megaOhms. And I would call that a high pH and low pH. At 16 MegaOhms it
is 6.1- 7.9. So, this "If your DI water has a high or low PH, it simply is no longer DI
water.", really isn't so, as no DI will ever get it to pH 7. You are talking about 100 %
pure water, which is made up of only H3O + and OH- and there is no such thing.

"And as for the PH meters, make sur you calibrate using two buffers. Using
one only moves the response up and down. "

This is no help for measuring RO/DI water

--
Boomer

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If You See Me Running You Better Catch-Up
"Robert Cadieux" wrote in message ...
:
: "Tre' Landrum" wrote in message
: news:5LCid.13517$233.3377@okepread05...
: OK, I really don't understand this statement "You can not check the pH of
: RO/DI water, with a pH meter or a test kit." You are measuring the among
: of
: H+ ions in the water. How does the lack of other ions have a negative
: effect
: on the pH measuring? I am working on my post doc... so feel free to use
: the
: big words. Thanks.
:
: Tre'
:
:
: Doesn't metter. If the DI water really is DI, the PH should be exactly
: 7.00. Although that is almost impossible to attain. DI water starts
: absorbing CO2 and the PH starts going down almost immediately unless you
: shield the water. If your DI water has a high or low PH, it simply is no
: longer DI water, plain and simple (with the exception of CO2 acidification
: of course which is reversible).
:
: And as for the PH meters, make sur you calibrate using two buffers. Using
: one only moves the response up and down. If it reads 5 at a PH of 6 and 6
: et a PH of 7, then adjusting the PH down by 1 unit will bring both PHs in
: line. However if it reads 4 in a 6 buffer and 7 in an 8 buffer, then the
: slope is also off. Using two buffers allows you to adjust both. Hard to
: explain with drawing a picture.
:
: Robert
:
: