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B.9.5.1.2. Quality Assurance <br /> The following information about the field measurement of specific conductance shall be logged <br /> for QA documentation: <br /> • Source and expiration date of standards <br /> • Instrument manufacturer and model number <br /> • Date and time of calibration check <br /> • Temperature and conductivity of standards used to check calibration <br /> • Sample temperature and conductivity reading <br /> • Name of person performing the measurement <br /> B.10. Standard Test Method for the Field Measurement of pH <br /> B.10.1. Introduction <br /> An accurate pH is critical for the prediction and interpretation of the reactions and migration of <br /> dissolved species. This procedure provides a useful pH measurement under most field <br /> situations. <br /> B.10.2. Scope <br /> This is the procedure for the measurement of pH in an aqueous solution. The pH is determined <br /> using a glass hydrogen-ion electrode compared to a reference electrode of known potential by <br /> means of a pH meter. <br /> B.10.3. Significance and Use <br /> The pH of a solution is defined as the negative logarithm to the base 10 of the hydrogen-ion <br /> activity in moles per liter: <br /> pH = — logio(a.H+) = login <br /> aH+1 <br /> Because pH is exponentially related to concentration, great care shall be taken in making the <br /> measurement. <br /> Natural waters usually have pH values in the range of 4 to 9. The primary control over pH in <br /> natural waters is the carbonate system, including gaseous and dissolved carbon dioxide, <br /> bicarbonate, and carbonate ions. <br /> Daub&Associates, Inc. Page B-25 Natural Soda LLC 2022 SAP <br />