The first period began in extremely remote prehistoric times; the second in the 14th century; and the third with the invention of the Bessemer process in 1856.
Selling his Baltimore works, he built, in 1836, in partnership with his brother Thomas, a rolling mill in New York; in 1845 he removed it to Trenton, New Jersey, where iron structural beams were first made in 1854 and the Bessemer process first tried in America in 1856; and at Philippsburg, New Jersey, he built the largest blast furnace in the country at that time.
The obstacle is that, owing to unavoidable irregularities in the blast-furnace process, the siliconand sulphur-content of the cast iron vary to a degree and with an abruptness which are inconvenient for any conversion process and intolerable for the Bessemer process.
In the basic Bessemer process phosphorus is readily removed by oxidation, because the product of its oxidation, phosphoric acid, P 2 O 5, in the presence of an excess of base forms stable phosphates of lime and iron which pass into the slag, making it valuable as an artificial manure.
Though all this is elementary to-day, not only was it unknown, indeed unguessed, at the time of the invention of the Bessemer process, but even when, nearly a quarter of a century later, a young English metallurgical chemist, Sidney Gilchrist Thomas (1850-1885), offered to the British Iron and Steel Institute a paper describing his success in dephosphoriz ing by the Bessemer process with a basic-lined converter and a basic slag, that body rejected it.
