THE BAs[(' ])ROCESS. The process of dephosphorizing iron in the Bessemer converter, held in this country under patents of Thomas, Snelus and Riley, is called, by common consent, the J3asic Process.
Ill the ordinary Bessemer operation, when the flame "drops," as observed by the naked eye, or when the carbon lines disappear, as more accurately observed through the spectroscope, there still remain in the metal some hundredths of a per cent. of carbon, also of" silicon, also ~dl the phosphorus which the metal originally ~:ontained. Further blowing would oxidize the iron itself'. But if the slag ill the converter, instead of being acid (chiefly silica), as in the ordinary operation, is basic (chiefly lime), a small part of' the phosphorus will be found in the slag, instead of in the metal, when the flame drops. And if the blowing is further continued ibr two or three minutes, all the phos-ph{~rus, excepting a few hundredths, will be tbund in the slag, and the iron will not have been much oxidized; it will have been protected by the phosphorus. Chemists disagree as to the precise re~/ctions which occur; we suppose that phosphorus is always 'oxidized by the air blast, and that it constantly returns to the iron, in presence of` an acid slag; we know that a basic slag retains the phosphorus, however it may have got it.
The basic process, therefore, consists of two things: First, the mainteuanee of a basic slag; second, the ':afterblow."
First. The basic slag is formed by the addition of about twen W per cent. of lime to the iron charge in the converter before or during the blowing. The basic slag is maintained chiefly By making the converter lining of" lime, and also by using iron low iu silicon. An acid lining would be destroyed by the lime additions, and would vitiate the slag. The latter result would be produced also by silica formed by the oxidation of the silicon in the iron. The grand {tifficul U has been tlle limited durabiti U of the basic lining. After much costly experimenting, practicable linings have been made of dolomite bricks