Date: Wed, 12 Nov 1997 07:53:57 -0500 From: Carl Gustafson <carl.gustafson@cbis.ece.drexel.edu> To: cp@opus.hpl.hp.com Message-Id: <aabcdefg4311$foo@default> Subject: Re: water pH
Perry Malouf wrote:
>Brandon wrote:
>
>> I've been watering all my plants with distilled water (pH ~6). Out of
>> curiosity, I just took the pH of the water in my cephalotus' dish and
>> found it to be about 7.2.
>
>Distilled water should have a pH of 7, which is neutral. How are you
>measuring the pH?
In the absence of any dissolved materials, distilled water should be pH
7.0. However, carbon dioxide is very soluble in water, and will immediately
drop pH below the neutral point. If I did my calculation correctly, only
1ppm of [dissolved and fully dissociated] CO2 is needed for a pH of
approximately 6.0.
In practice, it is difficult to impossible to get distilled water with a pH
of 7.0, and 6.0 is actually pretty good. Further, it is very difficult to
do an *accurate* measurement of the pH of distilled water, as almost
everything, including pH meter probes, can have a significant effect on the
pH of distilled water.
Carl G.
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