Distilled water Ph

[jc88usus]

I just got and calibrated my Ph tester. I set about testing my various solutions. What struck me as odd was that the distilled water I bought has a ph of between 4.0 and 5.3. Also, when I swirl the tester in the water some more the ph keeps dropping. Any clues what is up with that? I thought distilled water would be completely neutral.

[luminous]

Distilled water has little buffering capacity and will readily absorb gases from the atmosphere. One of the main absorbed gases is carbon dioxide, which dissolves into the water and forms carbonic acid. The carbonic acid is enough to lower the pH down in the 5 to 6 range. It's pretty common for distilled water to have the pH you measured.
Search the web for aquariums and fish will give you more than you ever wanted to know abot water...

steve

Originally Posted by jc88usus

I just got and calibrated my Ph tester. I set about testing my various solutions. What struck me as odd was that the distilled water I bought has a ph of between 4.0 and 5.3. Also, when I swirl the tester in the water some more the ph keeps dropping. Any clues what is up with that? I thought distilled water would be completely neutral.

[luminous]

Hmmm. just reread your post. down in the 4 range is pretty low to be explained by CO2 absorpton alone. 5.3 I might buy....

steve

[archimedes]

Greetings JC,
If I may; I would like to know if you also purchased the
buffer solutions with your Ph meter?
Was it your intent to use de-ionized water to calibrate
the Ph meter?

archi

and to Luminous, thanks for the excellent FYI on the
cause & effect analysis.

[jc88usus]

Thanks Archimedes, and yes, I did get the buffer solns. to calibrate with. It took a little fiddling back and forth to get the readings to 4.0 and 7.0, but it wasn't too bad. The worst part was finding a screwdriver small enough to fit in the hole.

mad