User manual EUTECH INSTRUMENTS SILVERSULFIDE EPOXY

[. . . ] Instruction Manual Silver/Silver Sulfide Electrode EUTECH INSTRUMENTS PTE LTD. INSTRUCTION MANUAL SILVER/SILVER SULFIDE ION ELECTRODE 1 Silver/Silver Sulfide Electrode Instruction Manual TABLE OF CONTENTS GENERAL INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Required Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Required Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] Place 100 ml of the sample and 2 ml of ISA in a 150 ml beaker, place it on the magnetic stirrer, and begin stirring. Immerse the electrode tips in the solution and wait for the reading to stabilize. Read the concentration directly from the meter display. The calibration should be checked every two hours. Assuming no change in ambient temperature, place the electrode tips in the first silver standard. After the reading has stabilized, compare it to the original reading in Step 4 above. A reading differing by more than 0. 5 mV or a change in the ambient temperature will necessitate the repetition of Steps 2-8 (9) above. The meter should be re-calibrated daily. 5. 8. 9. 10. 11. 12. Direct Measurement of Sulfide (using a pH/mV meter) 1. By serial dilution of the weekly standard, prepare three standard sulfide solutions. Measure out 50 ml of each standard into individual 150 ml beakers and add 25 ml of SAOB and 25 ml of distilled water to each. Place the most dilute solution on the magnetic stirrer and begin stirring at a constant rate. After assuring that the meter is in the mV mode, lower the electrode tips into the solution. When the reading has stabilized, record the mV reading. Place the midrange sulfide standard on the magnetic stirrer and begin stirring. After rinsing the electrodes with distilled water, blot dry and immerse the electrode tips in the solution. When the reading has stabilized, record the mV reading. 2. 3. 10 Instruction Manual Silver/Silver Sulfide Electrode 4. Place the most concentrated sulfide standard on the magnetic stirrer and begin stirring. After rinsing the electrodes with distilled water, blot dry and immerse the electrode tips in the solution. When the reading has stabilized, record the mV reading. Using the semi-logarithmic graph paper, plot the mV reading (linear axis) against concentration (log axis). A typical calibration curve can be found in Figure 1. 5. A calibration curve is constructed on semi-logarithmic paper when using a pH/mV meter in the millivolt mode. The measured electrode potential in mV (linear axis) is plotted against the standard concentration (log axis). In the linear region of the curve, only three standards are necessary to determine a calibration curve. [. . . ] Millivolt potentials occur from the inter-diffusion of ions in the two solutions. Electrode charge will be carried unequally across the solution boundary resulting in a potential difference between the two solutions, since ions diffuse at different rates. When making measurements, it is important to remember that this potential be the same when the reference is in the standardizing solution as well as in the sample solution or the change in liquid junction potential will appear as an error in the measured electrode potential. 21 Silver/Silver Sulfide Electrode Instruction Manual The composition of the liquid junction filling solution in the reference electrode is most important. The speed with which the positive and negative ions in the filling solutions diffuse into the sample should be as nearly equal as possible, that is, the filling solution should be equitransferent. [. . . ]