The design and performance of reference electrodes for use in high subcritical and supercritical aqueous systems are reviewed. Particular attention is paid to the stability of the electrochemically active elements, to the contribution of the two irreversible thermodynamic potentials (the isothermal liquid junction potential and the thermal liquid junction potential) to the measured potential, to calibration of the reference electrode on to the standard hydrogen scale, and to the application of the electrodes in pH measurements and in potentiometry. Methods for estimating and suppressing the thermal diffusion potential and the isothermal liquid junction potential are also discussed. While significant progress has been made over the past several decades in developing viable reference electrodes for use in high temperature aqueous systems, particularly for potential monitoring in subcritical systems, no universally accepted reference electrode has emerged for potential monitoring in supercritical aqueous systems.

Subject
Electrochemical cells, Diffusion, Reference electrodes, Aqueous solutions, Potential measurements, Acidity, Liquids, Potassium chloride, Elements, Electrodes, Electrolytes, Electrode potential, Hydrogen
Keywords:
Reference electrodes, subcritical aqueous systems, supercritical aqueous systems, thermal diffusion, pH measurement
© 2005 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2005
Association for Materials Protection and Performance (AMPP)
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