Standard Test Methods for pH Measurement of Water of Low Conductivity

1.1 These test methods are applicable to determine the pH of water samples with a conductivity lower than 100 µ S/cm (see Annex A1 and Table A1.1 and Table A1.2 ) over the pH range of 3 to 11 (see Fig. 1). pH measurements of water of low conductivity are problematical (see Annex A2). Specifically, these test methods avoid contamination of the sample with atmospheric gases (see Section 7) and prevent volatile components of the sample from escaping. These test methods provide for pH electrodes and apparatus that address the considerations discussed in Annex A2. These test methods also minimize problems associated with the sample's pH temperature coefficient when the operator uses these test methods to calibrate an on-line pH monitor or controller (see Appendix X1). Two test methods are given as follows:

1.2 Test Method A covers the precise measurement of pH in water of low conductivity utilizing a real-time, short duration, flowing sample procedure.

1.3 Test Method B covers the measurement of pH in water of low conductivity with a lower limit of 2.0 S/cm, utilizing a static grab-sample procedure where it is not practicable to take a real-time flowing sample.

Note 1--Test Method A is preferred over Test Method B whenever possible. Test Method A is not subject to the limited conductivity range, temperature interferences, potential KCl contamination, and time limitations found with Test Method B.

1.4 The values stated in SI units are to be regarded as standard.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.