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Percy Carlyle Gilchrist (1851-1935) was a metallurgist, cousin of Sidney Gilchrist Thomas.
Gilchrist worked at Blaenavon Ironworks
1875 Thomas communicated the details of his ideas for improving the steel making process to his cousin Percy Gilchrist, then chemist at the Blaenavon Ironworks, and experiments were made which proved satisfactory. This led to the Thomas-Gilchrist process.
1935 Obituary 
PERCY CARLYLE GILCHRIST, F.R.S., was one of the most notable pioneers in the manufacture of basic steel. With his cousin, Mr. Sydney Gilchrist Thomas, he developed the method of production which was afterwards known as the Thomas and Gilchrist process.
Mr. Gilchrist was born at Lyme Regis in 1851 and entered the Royal School of Mines, South Kensington, in 1868, obtaining his associateship three years later.
From 1871 to 1876 he was chemist to a copper-mining firm at Cwm Avon, after which he joined the Blaenavon Iron and Steel Works in a similar capacity. Shortly afterwards he commenced his collaboration with his cousin, their aim being to develop a process for eliminating phosphorus from Bessemer steel, by lining the converters with basic instead of acid (siliceous) material. The project was materially assisted by Mr. Edward P. Martin, M.I.Mech.E. (Past-President), and the first patent was taken out in 1877.
In the following year a great improvement was effected by substituting a hard flinty material for the comparatively soft lining first adopted. Mr. E. Windsor Richards, M.I.Mech.E. (Past-President), then manager of Messrs. Bolckow, Vaughan and Company, Ltd., of Middlesbrough, saw the possibilities of the process and invited Mr. Gilchrist and Mr. Thomas to design an experimental plant for his firm. This they did, and in 1879 two 30 cwt. converters were put into service.
Three years later the Dephosphorizing and Basic Patents Company, Ltd., was formed, Mr. Gilchrist and Mr. Thomas being among the original members, with the object of merging the various interests concerned.
On the death of Mr. Thomas in 1885, Mr. Gilchrist became managing director of the company and continued his work in developing the process; in addition, he acted as a consulting metallurgical engineer.
In 1891 he was elected a Fellow of the Royal Society.
The basic steel process was widely adopted abroad, especially in France, and Mr. Gilchrist was made a Chevalier of the Legion of Honour.
He was one of the oldest Members of the Institution, having been elected in 1883. In addition he was a Member of the Institution of Civil Engineers, and in 1916 he was made an honorary vice-president of the Iron and Steel Institute, before which he had read several papers describing his process.
He lived in retirement for many years, and died on 15th December 1935, in his eighty-fourth year.