METALLURGY OF CAST IRON.
exceed .10, lower phosphorus ores must be used than in making foundry irons. It is often found beneficial to have pig iron contain as high as 1.50 phosphorus, owing to the fact that phosphorus possesses the quality of giving life and fluidity to molten metal, which is most desirable in running thin castings.
For de-phosphorizing magnetic ores, different kinds of devices have been used. Fig. 5 will convey an idea of the principles involved in the separation of " tailings '' and '' concentrates " by the employment of magnetic power. By the use of separators or magnets from 50 per cent to So per cent of the phosphorus originally c o n -tained in ore is said to be removed. Magnetic ores which contain pyrites (which is a combination of 53.3 per cent of sulphur with 46.7 per cent of iron) can have, it is also said, a larger per cent of their sulphur contents removed by magnetic concentration with a separator than by roasting, as referred to below. Sometimes the sulphur is present in pyrrho-tite (which is 39.5 per cent of sulphur combined with 60.5 per cent of iron) in which state experiments have shown that there would be as much sulphur in the con-
FIG. 5.óBUCHANAN SEPARATOR. !