Blast furnace slag, a by-product in the manufacture of pig
iron from ores, contains a significant amount of
phosphorus. This phosphorus is removed by adding lime
or calcium carbonate to the converter. The phosphorus
oxide formed combines with calcium oxide and silica to
form a slag on top of the molten iron. The slag is then
removed, cooled and powdered and is used for liming
acid soils. Depending on the process of steel
manufacture, the slag is called Bessemer basic slag or
open-hearth basic slag.
