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PH Seminar

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PH Seminar

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    1. pH Seminar Thermo Electron Corporation Water Analysis Beverly, MA

    2. What Is pH? pH by definition is the hydrogen ion activity Activity may be thought of as the “free” ion rather than total Anything that gives more H+ than HOH is acid Anything that gives less H+ than HOH is alkaline (basic)

    3. What Is pH? The pH scale Each pH unit is a factor of 10 [H+]

    4. pH Measuring System The pH meter measures the voltage potential (mV) difference between the inside of the pH electrode and the outside sample (reference)

    5. pH Meters What is a pH meter? Acts as a volt meter Translates electrode potential (mV) to pH scale Meter functions Stores calibration curve Adjusts for temperature changes Adjusts electrode slope Signals when reading is stable

    6. pH Meters Features mV and relative mV Autocalibration/autobuffer recognition Number of calibration points Display information RS232 or recorder outputs Datalogging GLP

    7. How Is pH Measured? Glass pH electrodes develop a voltage across the permeable glass membrane The voltage is related to the difference in H+ activity inside and outside the glass

    8. pH Electrode Filling solution typical composition: Buffer solution KCl Saturated AgCl Typical internal reference: Ag/AgCl

    9. Electrode References Calomel reference Fixed Hg2++ activity in contact with Hg Hg2Cl2

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