Paul-Louis-Toussaint Héroult (1863-1914) had already developed an interest in the extraction of aluminium at the age of 15 after reading Henri Sainte-Claire Devilles treatise on aluminium. After graduating from the École des Mines in Paris he conducted experiments in his fathers tannery which culminated in his being granted a French patent for fused-salt electrolysis on 23 April 1886. If aluminium oxide is dissolved in molten cryolite, it dissociates on passage of a direct electrical current. Following a protracted legal dispute with the American Charles Martin Hall, who had discovered an identical process in the same year, Hall was granted a patent for the USA and Héroult"s claims were recognised for all other countries.
In 1887 Héroult built the first plant based on his patent at Neuhausen am Rheinfall in Switzerland, for Swiss investors, which was the forerunner of Aluminiumindustrie AG (AIAG). In 1888 he returned to Paris and was co-founder of the French aluminium industry. The process made cheap extraction and thus widespread use possible for the first time. Todays production is still based on this process.
Héroult did not sit back and enjoy the affluence he had gained but worked with great perseverance on important improvements to the process, for example a significant increase in efficiency by using large-surface anodes for the power supply. In 1898 he designed the first industrial-scale electric arc melting furnace for steel production based on the invention of Wilhelm Siemens of 1878.