Compositions whose conductance is essentially ionic have been prepared in the and systems. The maximum conductance is attained at a ratio of silver iodide to alkali cyanide of four to one. For example, has a conductance of ohm−1 cm−1 at 25°C. The conductance has been measured as a function of temperature for and of composition for the general system. X‐ray patterns and thermal analyses indicate that these new compounds are unique materials and not mixtures of their constituents.