A Study on the Precise End-Point Detection in Titration by Using the Phase Angle Measurements

위상각 측정에 의한 적정의 정확한 종말점 검출법에 관한 연구

  • Park, Byung-Bin (Department of Chemistry, Kongju National University) ;
  • Shin, Ho-Sang (Department of Environmental Education, Kongju National University) ;
  • Lee, Han-Hyoung (Department of Chemistry, Kongju National University)
  • 박병빈 (공주대학교 자연과학대학 화학과) ;
  • 신호상 (공주대학교 사범대학 환경교육과) ;
  • 이한형 (공주대학교 자연과학대학 화학과)
  • Received : 1999.03.09
  • Published : 1999.08.25

Abstract

A study on the application of impedance phase angle for redox titration, acid-base titration, chelate titration and precipitation titration has been carried out. A constant alternating current was passed between two platinum electrodes. One of them was a polarizable micro-electrode of $0.1cm^2$ or $0.026cm^2$ surface area and the other a non-polarizable large electrode of $1cm^2$ surface area dipped in the solution to be titrated. The impedance and the phase angle of the titration cell were measured with lock-in amplifier to obtain well behaved titration curve respectively. In titration of oxalic acid vs. potassium permanganate, the end-point was obtained successfully from the phase angle titration curve. In this experiment, the concentration of 0.0005 M to 0.05 M, the current of $50{\mu}A$ and the frequency of near 50 Hz were used. In titration of phosphoric acid vs. sodium hydroxide, the first end-point was obtained successfully on the optimum experimental condition of 0.001 M concentration, $50{\mu}A$ current and 25~97 Hz frequency. However, the end-point in titration of cupric sulfate vs. disodium-EDTA couldn't be obtained clearly. The end-point was obtained with the out-of-phase impedance curve on the experimental condition of 0.01 M concentration, $100{\mu}A$ current, 5~35 Hz frequency range. In titration of sodium chloride vs. silver nitrate, the end-point was obtained successfully on the experimental condition of 0.1 M concentration, $100{\mu}A$ current and 5~47 Hz frequency range. This study showed that the impedance phase angle was applicable for the detection of the end-points in redox titration curve, acid-base titration curve, chelate titration curve and precipitation titration curve.

Keywords

impedance phase angle;end-point;titration curve

References

  1. 전기화학측정법 T. Osaka;N. Oyama;T. Ohsaka
  2. Electrochemical Methods-Fundamentals and Application J. B. Allen;L. R. Faulkner
  3. J. Electrochem. Soc: Electrochem. Scinence and Technology v.124 no.11 A. A. Pilla;G. S. Margules
  4. J. Electroanal. Chem. v.8 U. H. Narayanan;G. Dorairaj;Y. M. Iyer
  5. J. Electroanal. Chem. v.2 K. S. Narayanan;H. C. Gaur
  6. J. Korean Society of Analytical Science v.3 no.3 B. B. Park;T. Watanabe
  7. J. Electrochem. Soc: Electrochem. Sci. v.117 no.4 A. A. Pilla
  8. Electrochemistry;Principles: Methods and Application C. M. A. Brett;A. M. O Brett
  9. Electrochemical Chemistry B. H. Vassos;G. W. Ewing
  10. Quantitative Chemical Analysis K. Sandell;M. Bruckenstein
  11. Electrochemistry for Chemist's D. T. Sawyer;A. J. L. Roberts, Jr.
  12. J. Electroanal. Chem. v.6 K. S. Narayanan;C. P. Namboodiripad
  13. Laboratory Techniques in Electroanalytical Chemistry P. T. Kissinger;W. P. Heineman
  14. 화학의세계 v.33 no.12 박수문
  15. Electroanalytical Chemistry v.4 A. J. Bard
  16. Fundamentals of Electrochemical Science H. B. Oldham;J. C. Myland