Héroult, Paul Louis Toussaint

SUBJECT AREA: Metallurgy

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b. 1863 Thury-Harcourt, Caen, France

d. 9 May 1914 Antibes, France

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French metallurigst, inventor of the process of aluminium reduction by electrolysis.

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Paul Héroult, the son of a tanner, at the age of 16, while still at school in Caen, read Deville's book on aluminium and became obsessed with the idea of developing a cheap way of producing this metal. After his family moved to Gentillysur-Bièvre he studied at the Ecole Sainte-Barbe in Paris and then returned to Caen to work in the laboratory of his father's tannery. His first patent, filed in February and granted on 23 April 1886, described an invention almost identical to that of C.M. Hall : "the electrolysis of alumina dissolved in molten cryolite into which the current is introduced through suitable electrodes. The cryolite is not consumed." Early in 1887 Héroult attempted to obtain the support of Alfred Rangod Pechiney, the proprietor of the works at Salindres where Deville's process for making sodium-reduced aluminium was still being operated. Pechiney persuaded Héroult to modify his electrolytic process by using a cathode of molten copper, thus making it possible produce aluminium bronze rather than pure aluminium. Héroult then approached the Swiss firm J.G.Nehe Söhne, ironmasters, whose works at the Falls of Schaffhausen obtained power from the Rhine. They were looking for a new metallurgical process requiring large quantities of cheap hydroelectric power and Héroult's process seemed suitable. In 1887 they established the Société Metallurgique Suisse to test Héroult's process. Héroult became Technical Director and went to the USA to defend his patents against those of Hall. During his absence the Schaffhausen trials were successfully completed, and on 18 November 1888 the Société Metallurgique combined with the German AEG group, Oerlikon and Escher Wyss, to establish the Aluminium Industrie Aktiengesellschaft Neuhausen. In the early electrolytic baths it was occasionally found that arcs between the bath surface and electrode could develop if the electrodes were inadvertently raised. From this observation, Héroult and M.Killiani developed the electric arc furnace. In this, arcs were intentionally formed between the surface of the charge and several electrodes, each connected to a different pole of the AC supply. This furnace, the prototype of the modern electric steel furnace, was first used for the direct reduction of iron ore at La Praz in 1903. This work was undertaken for the Canadian Government, for whom Héroult subsequently designed a 5,000-amp single-phase furnace which was installed and tested at Sault-Sainte-Marie in Ontario and successfully used for smelting magnetite ore.

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Further Reading

Aluminium Industrie Aktiengesellschaft Neuhausen, 1938, The History of the Aluminium-Industrie-Aktien-Gesellschaft Neuhausen 1888–1938, 2 vols, Neuhausen.

C.J.Gignoux, Histoire d'une entreprise française. "The Hall-Héroult affair", 1961, Metal Bulletin (14 April):1–4.

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