On 12 Mar, 05:41, wrote:

I thought that this article might interest this group.

http://www.keepingfish.com/pageMain....d=DisplayArtic...

To quote:

The meter works by hydrogen ions passing through
the humid air until they are balanced.

There is no such animal as "hydrogen ions passing through the humid
air". What can be exchanged is pure water (think in terms of
distillation - evaporation/condensation) and carbon dioxide (plus
other gases, which won't change solution pH). Relying on CO2
equilibrium for pH measurements doesn't look like a reliable idea to
me - it may work only as long as CO2 is the only reason for pH
changes.

Best regards,
Borek
--
http://www.ph-meter.info
http://www.chembuddy.com