text: Sidney Gilchrist Thomas, a Londoner with a Welsh father, was an industrial chemist who decided to tackle the problem of phosphorus in iron, which resulted in the production of low grade steel. Believing that he had discovered a solution, he contacted his cousin, Percy Gilchrist, who was a chemist at the Blaenavon Ironworks. The manager at the time, Edward Martin, offered Sidney equipment for large-scale testing and helped him draw up a patent that was taken out in May 1878. Sidney Gilchrist Thomass invention consisted of using dolomite or sometimes limestone linings for the Bessemer converter rather than clay, and it became known as the basic Bessemer rather than the acid' Bessemer process. An additional advantage was that the processes formed more slag in the converter, and this could be recovered and used very profitably as a phosphate fertilizer.