No. 18

References:

1. "Standard Practice for Oxidation-Reduction Potential of Water", ASTM D 1498 - 00.
2. "Expressions of Performance of Electrochemical Analyzers", International Standard IEC 746-5.
3. "T-611 Analysis, Redox Potential", Turo 07/03/2001 (Bulletin 19).

Oxidation -Reduction Potential of Water  

 There are two ways of reporting oxidation-reduction potential.

One way to to report the REDOX potential as the dirct voltage that was measured. Turo instruments used the ASTM standard for this method until early 2001.

The other way is to report the REDOX potential with it referred to the hydrogen electrode. Part 13 of the ASTM standard states that reporting can be either the direct voltage (see section 13.1) or referred to the hydrogen electrode (see section 13.2).

Since early 2001 Turo instruments have reported the REDOX potential as referred to the hydrogen electrode. Bulletin 19 ("T-611 Analysis, Redox Potential")  explains the reasoning behind this. IEC standard 746 is used as the basis for this.