pH

Surface tension method

Conductance method

3

0.0040

0.0044

4

0.0032

0.0038

5

0.0025

0.0023

6

0.0023

0.0021

7

0.0022

0.0020

8

0.0022

0.0020

9

0.0022

0.0020

10

0.0022

0.0020