Percy Carlyle Gilchrist FRS (27 December 1851 – 16 December 1935) was a British chemist and metallurgist.He was born in Lyme Regis, Dorset, the son of Alexander and Anne Gilchrist and studied at Felsted and the Royal School of Mines. He is best known for his collaboration with his cousin, Sidney Gilchrist Thomas on what became the standard "basic process" for making steel. This enabled the production of low-phosphorus steel from local high-phosphorus ores by changing the standard acidic process to a basic process which meant that steel became cheaply available to British industry — low phosphorus ores being available by importation only. He developed the process in 1875-77 together with his cousin. It involved melting pig iron in a converter similar to that used in the Bessemer process and subjecting it to prolonged blowing. The oxygen in the blast of air oxidized carbon and other impurities, and the addition of lime at this stage caused the oxides to separate out as a slag on the surface of the molten metal. A side benefit was that the phosphorus containing slag could be used as an agricultural fertilizer.He was elected vice-president of the Iron and Steel Institute and in 1891 a Fellow of the Royal Society. He died in 1935. He had married Nora, the daughter of Captain L N Fitzmaurice RN.