What is the influence for conductivity and pH if the temperature changed? Thanks.

 

For pH, there are 3 factors.

1. The dissociation of H2O into H+ and OH- ions depends on temperature. At 0 degC, the dissociation is 3.38 x 10^-8 mol/litre; at 25 decG 1 x 10^-7; at 50 degC 2.34 x 10^-7. This gives a pH of 7.47 at 0 decG, 7 at 25 degC, 6.63 at 50 degC.

2. Since water expands when it is heated, the concentration will all slightly as temperature rises. This will slightly increase the apparent pH.

3. The Nernst equation governs the development of a voltage from pH. This voltage is 0.1984 T (pH2 - pH1) where T is the absolute temperature. So the
voltage per pH point will range from 54.20 to 74.04 mV/pH over the temperature range from 0 degC to 100 degC. For conductivity, temperature also has an effect. As the temperature of the
material increases, ion velocity increases, and the number of ions may also increase. The change in conductivity with temperature will vary from 5%/ºC for pure water to a little less than 2%/ºC with weak electrolytes and somewhat lower for strong electrolytes.

Hope this helps,
Bruce

 

Has anyone got good data for either saturated steam or superheated water? I see conductivity vs. temp curves but all end at 100C.

Logic may say the 2% rule continues, but water is not known to be a normal fluid.