	Charles Pollak (born Karol Pollak), a producer of accumulators, found out that the oxide layer on an aluminum anode remained stable in a neutral or alkaline electrolyte, even when the power was switched off. In 1896 he filed a patent for an "Electric liquid capacitor with aluminum electrodes" (de: "Elektrischer Flüssigkeitskondensator mit Aluminiumelektroden") based on his idea of using the oxide layer in a polarized capacitor in combination with a neutral or slightly alkaline electrolyte.