[Aquattro]

Darren, I meant that the second electrode provides the difference rating from the detected ions. Although ionic activity is low in pure water, there is an abundance of hydronium and hydroxyl ions...that's what water is. Even distilled water has a [H+] of -log of 1 x 10^7. I figured this could be detected. My thinking is that without ionic interference from other species, it would be easier. Not saying I was right, just didn't make immediate sense to me. Gonna have to dig up the chem books [img]images/smiles/icon_confused.gif[/img]