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
