Does your pH meter have a temperature compensation function? Paul -------------- Original message --------------
> Olga Caussade asked why her water has a pH of 6.5 when stored in the dark, > but has a pH of 5 and is 10 degrees C warmer when kept in the light. > > Olga, I tried doing the maths & your numbers didn't work out. Basically, the > pH of any sample of water varies with the temperature. As the temperature > rises, the pH decreases because the solution becomes more acidic, and it > becomes less acidic as the temperature falls, which is what you observed. > Unfortunately, you'd need a hell of a lot more than a 10 degree rise to drop > the pH by 1.5 degrees, so something else must be happening in your water. > > Water always contains dissolved carbon dioxide, which makes it acidic. As > the temp rises, less carbon dioxide dissolves, so the pH rises (water > becomes less acidic). This effect runs in the opposite direction to the > pH/temperature effect, and if my assumptions about your water and maths are > right, this would more or less cancel out the drop in pH caused by your 10 > degree temp rise. > > Conclusion; something else is causing your pH change. Have you got any algae > or other plants growing in your container ? They would proliferate in the > light, respiring and giving off carbon dioxide, which would dissolve in the > water, making it more acidic. > > Cheers, > > Peter O'Byrne > _______________________________________________ > the OrchidGuide Digest (OGD) > [EMAIL PROTECTED] > http://lists.orchidguide.com/mailman/listinfo/orchids
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