(EP917716-A1)      The proton conductor (I) contains 1-99 wt.% acid and 99-1 wt.% amphoteric substance (II) and is thermostable at temperatures up to 400C.    Also claimed are: (a) a membrane containing (I), resistant to temperatures up to 400C; and (b) methods for producing (I) and the membrane.    USE -   (I) is used for coating sheet materials, especially membranes, foils and electrodes; and the membranes are used in secondary batteries, electrochromic displays or electrochemical cells (all claimed), including fuel cells.    ADVANTAGE -   Known proton conductors resistant to temperature above 100C have limitations. Mixtures of oxo-acids or salts with anhydrous amphoteric substances are useful only at ca. 200C and have unsatisfactory power/weight and power/volume ratio for mobile applications, whilst oxides, hydroxides and apatites have satisfactory proton conductivity only above 500C. Polymer electrolyte membranes are useful only up to 100C. (I) have good proton conductivity over a wide temperature range and high chemical, electrochemical and physical stability, are resistant to chemical attack by acids and bases and to both high and low temperatures. Their large power/volume and power/weight ratios, with values of &gt; 300 W/l, preferably &gt; 350 W/l and &gt; 150 W/kg, preferably &gt; 190 W/kg in a fuel cell stack.    (JP2000517462-W)      The proton conductor (I) contains 1-99 wt.% acid and 99-1 wt.% amphoteric substance (II) and is thermostable at temperatures up to 400C.    Also claimed are: (a) a membrane containing (I), resistant to temperatures up to 400C; and (b) methods for producing (I) and the membrane.    USE -   (I) is used for coating sheet materials, especially membranes, foils and electrodes; and the membranes are used in secondary batteries, electrochromic displays or electrochemical cells (all claimed), including fuel cells.    ADVANTAGE -   Known proton conductors resistant to temperature above 100C have limitations. Mixtures of oxo-acids or salts with anhydrous amphoteric substances are useful only at ca. 200C and have unsatisfactory power/weight and power/volume ratio for mobile applications, whilst oxides, hydroxides and apatites have satisfactory proton conductivity only above 500C. Polymer electrolyte membranes are useful only up to 100C. (I) have good proton conductivity over a wide temperature range and high chemical, electrochemical and physical stability, are resistant to chemical attack by acids and bases and to both high and low temperatures. Their large power/volume and power/weight ratios, with values of &gt; 300 W/l, preferably &gt; 350 W/l and &gt; 150 W/kg, preferably &gt; 190 W/kg in a fuel cell stack.    (US6264857-B1)      The proton conductor (I) contains 1-99 wt.% acid and 99-1 wt.% amphoteric substance (II) and is thermostable at temperatures up to 400C.    Also claimed are: (a) a membrane containing (I), resistant to temperatures up to 400C; and (b) methods for producing (I) and the membrane.    USE -   (I) is used for coating sheet materials, especially membranes, foils and electrodes; and the membranes are used in secondary batteries, electrochromic displays or electrochemical cells (all claimed), including fuel cells.    ADVANTAGE -   Known proton conductors resistant to temperature above 100C have limitations. Mixtures of oxo-acids or salts with anhydrous amphoteric substances are useful only at ca. 200C and have unsatisfactory power/weight and power/volume ratio for mobile applications, whilst oxides, hydroxides and apatites have satisfactory proton conductivity only above 500C. Polymer electrolyte membranes are useful only up to 100C. (I) have good proton conductivity over a wide temperature range and high chemical, electrochemical and physical stability, are resistant to chemical attack by acids and bases and to both high and low temperatures. Their large power/volume and power/weight ratios, with values of &gt; 300 W/l, preferably &gt; 350 W/l and &gt; 150 W/kg, preferably &gt; 190 W/kg in a fuel cell stack.