Before 1856 when Bessemer announced his converter process, steel was made by melting cemented bars of malleable iron in small crucibles. The product was expensive and cost the equivalent of titanium sponge today. Bessemer's invention opened the way to the large-scale production of cheap steel, but it was soon found unsuitable for most irons because it failed to remove phosphorous. Bessemer attempted to eliminate the phosphorous but met with no success. In 1870 Sidney Thomas applied himself to the problem, and soon discovered that phosphorous could be removed into a slag provided sufficient lime was present to hold the phosphorous as phosphate. With the help of his cousin Percy Gilchrist, Thomas ran work trials and in 1878 they brought the process to success. Out of their work came the use of basic refractories and basic slags. As these improved the removal of phosphorous and sulphur in steelmaking became progressively more effective. In recent times ladle treatments have become important for obtaining specially low concentrations of phosphorus and sulphur in both hot metal and steel. New reagents such as magnesium-coke, calcium carbides, calcium silicide, and rare earth metals have come into use, these often being added by neutral-gas injection. -- AATA