8 Year No Water Change Experiment Result

[HuduVudu]

Adding totally pure fresh water (at pH 7.0 ) to seawater (at, say, pH 8.1) raises the pH above pH 8.1 for well understand, if not intuitive reasons.

The reason is that bicarbonate is a stronger acid in seawater than in fresh water. Adding fresh water makes it a weaker acid, and raises the pH by this reaction:

CO3-- + H+ --> HCO3-

It's counter-intuitive that the PH will rise, but it doesn't detract from my point that parameters have changed and the test my not be designed to work accurately under those parameters.

 

[Randy Holmes-Farley]

It's counter-intuitive that the PH will rise, but it doesn't detract from my point that parameters have changed and the test my not be designed to work accurately under those parameters.

Certainly true, and in fact, salinity has a big effect on nitrate testing due to chloride interference.

That is one reason why it took so long for Hanna to come up with a nitrate tester.