Aluminium encyclopaedia

Hall, Charles Martin

Charles Martin Hall (1863-1914) had already been involved with the extraction of aluminium as a chemistry student. After graduating in 1885 he continued to use the university laboratory in Ohio and in 1886 he discovered fused-salt electrolysis: aluminium oxide dissolved in molten cryolite decomposes when a direct current is passed through it. On 9 July 1886 he applied for a US patent. This was contested in 1887 by a Frenchman, Paul-Louis-Toussaint Héroult, who had already received a French patent for a practically identical process on 23 April 1886. Hall was subsequently granted a US patent because he had carried out his tests on American soil and could prove that he had carried these out before the date of Héroult"s patent application. Héroult"s patent claim was accepted in all other countries.

The fact that Hall and Héroult discovered the same process independently of each other is attributable to their both having knowledge of a book written by Sainte-Claire Deville in which he had already described this idea in 1859. Hall and Héroult had a number of other things in common: they were born in the same year and died in the same year, the perseverance with which they developed their inventions through to their technical operational feasibility and the wealth it brought them.

Hall recognised immediately the value of his invention, namely making extraction possible at a low price for the first time ever. Together with businessmen he founded the Pittsburgh Reduction Company in 1888 which was renamed Aluminum Company of America (Alcoa) in 1907 and up until the Second World War was synonymous with the aluminium industry in the USA.