Ekeberg isolated tantalum from Swedish ores in 1802 and gave it its name, that of the son of Zeus and the father of Niobé. Separation from niobium, with which it is always associated in ores, proved very difficult, being achieved by Marignac only in 1866. In 1903 von Bolton succeeded in producing tantalum powders by reduction of the double tantalum–potassium salt K2TaF7 with sodium. In the same year Siemens and Halske developed the first incandescent lamps in which a tantalum filament was substituted for the traditional carbon filament. In 1907 the same scientists used tantalum in rectifiers. Tantalum sheets for the chemical industry were introduced around 1930.