Thomas, Sidney Gilchrist

SUBJECT AREA: Metallurgy

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b. 16 April 1850 London, England

d. 1 February 1885 Paris, France

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English inventor of basic steelmaking.

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Thomas was educated at Dulwich College and from the age of 17, for the next twelve years, he made his living as a police-court clerk, although he studied chemistry in his spare time as an evening student at Birkbeck College, London. While there, he heard of the difficulties encountered by the Bessemer steelmaking process, which at that time was limited to using phosphorus-free iron. Any of this element present in the iron was oxidized to phosphoric acid, which would not react with the acidic lining in the converter, with the result that it would remain in the iron and render it too brittle to use. Unfortunately, phosphoric iron ores are more common than those free of this harmful element. Thomas was attracted by the view that a fortune awaited anyone who could solve this problem, and was not discouraged by the failure of several august figures in the industry, including Siemens and Lowthian Bell.

Thomas's knowledge of chemistry taught him that whereas an acidic lining allowed the phosphorus to remain in the iron, a basic lining would react with it to form part of the slag, which could then be tapped off. His experiments to find a suitable material were conducted in difficult conditions, in his spare time with meagre apparatus. Finally he found that a converter lined with dolomite, a form of limestone, would succeed, and he appealed to his cousin Percy Carlyle Gilchrist, Chemist at the Blaenavon Ironworks in Monmouthshire, for help in carrying out pilot-scale trials. In 1879 he gave up his police-court job to devote himself to the work, and in the same year they patented the Thomas- Gilchrist process. The first licence to use it was granted to Bolckow, Vaughan \& Co. of Middlesborough, and there the first steel was made in a basic Bessemer converter on 4 April 1879. The process was rapidly taken up and spread widely in Europe and beyond and was applied to other furnaces. Thomas made a fortune, but his health did not long allow him to enjoy it, for he died at the early age of 34.

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Bibliography

Further Reading

L.G.Thompson, 1940, Sidney Gilchrist Thomas, an Invention and Its Consequences, London: Faber.

T.G.Davies, 1978, Blaenavon and Sidney Gilchrist Thomas, Sheffield: Historical Metallurgy Society.

LRD