ASTM D 5464:2025

1.1 This test method is applicable to determine the pH of water samples with a conductivity of 2 μS/cm to 100 μS/cm over the pH range of 3 to 11 and is frequently used in power generation low conductivity samples. pH measurements of water of low conductivity are problematic. Specifically, this test method avoids contamination of the sample with atmospheric gases and prevents volatile components of the sample from escaping. This test method provides for pH electrodes and apparatus that address additional considerations discussed in Annex A2 . This test method also minimizes problems associated with the sample's pH temperature coefficient when the operator uses this test method to calibrate an on-line pH monitor or controller (see Appendix X1 ). 1.2 This test method covers the measurement of pH in water of low conductivity with a lower limit of 2.0 μS/cm, utilizing a static grab-sample procedure where it is not practicable to take a real-time flowing sample. Note 1: Test Method D5128 for on-line measurement is preferred over this method whenever possible. Test Method D5128 is not subject to the limited conductivity range, temperature interferences, potential KCl contamination, and time limitations found with this method. 1.3 For on-line measurements in water with conductivity of 100 μS/cm and higher, see Test Method D6569 . 1.4 For laboratory measurements in water with conductivity of 100 μS/cm and higher, see Test Method D1293 . 1.5 The values stated in SI units are to be regarded as standard. 1.6 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

13.060.50