Glass membrane electrodes with solid-state internal contacts for pH and pNa measurements

Abstract

The manufacture and properties of novel glass electrodes with solid-state contacts are described. The electrodes consist of spherical electrode membranes made of two different kinds of glass. The thin membrane in contact with the measured medium consists of an ion-selective electrolytically conducting material such as pH or pNa glass, whereas the other glass is a mixed Conducton This latter part of the double membrane uses electron- and ion-conducting mechanisms and is silver-coated. The mixed conduction glass and its metallic coating together form the internal discharge system of the ion-selective electrode. Investigation of the electrode function and the stability of its potendal has shown that its measuring characterisdcs are substantially better than those of glass electrodes with an internally metal-coated membrane. The reason for this is that reversible Charge carrier transitions (redox reactions) are possible at all phase boundaries. The electron transition is brought about by a change in the conduction mechanism from ionic conduction to electronic conduction. From the position of the isotherm intersection points outside the utilizable measuring ränge of the electrodes, it follows that automatic temperature compensation is not possible.