Abstract:A solid electrolyte tube was made with Sr_0.69La_0.31F_2.31+SrS co-precipitated powder mixed with 3 wt. -% SrS solid powder. The cell, W|W , WS2|Sr_0.69La_0.31F_2.31+SrS |[S]_Cu|W , was designed to determine the sulphur activity in liquid copper. The EMF was stable and the cell was reversible. The results of determination conformed with those measured by other authors. The material of Sr_0.69La_0.31F_2.31+SrS can be used to make solid electrolyte sensor for sulphur in high temperature   melts.

Key words: solid electrolyte; electrochemical sensor; sulphur activity;