Abstract: A novel series of chalcogenide glass compositions that are relatively highly selective for a specific ion in solution. When utilized as a sensing element for electrodes or similar analytical devices, a modified surface layer is formed on the surface of the glass in contact with the test solution. The surface layer being characterized by a surface ionic conductivity ranging from 10.sup.-7 to 10.sup.-2 S/cm, a diffusion coefficient ranging from 10.sup.-11 to 10.sup.-6 cm.sup.2 /s and having a ratio of electronic to ionic conductivity within the modified surface layer of not more than 1.0. Specific compositions having these unique morphology and transport properties are disclosed for the detection of cadmium, silver, thallium, mercury, copper and lead.

Abstract: An improved "all solid state" ion selective electrode device comprising a unique sensing element of triple-layer membrane construction. The first sensor layer of the sensing membrane comprising a solid electrolyte composition, the middle layer comprising a mixture of the aforesaid electrolyte composition and finely divided electronic conducting material, and the third contacting layer composed principally of the aforesaid electronic conducting material. The middle layer having a gradient of component concentration such that a substantial amount of the electrolyte composition is presented in the middle layer closest the first sensor layer and a substantial amount of the electronic conducting material is presented in the middle layer closest the third contacting layer.