Soft Pig Iron
This iron is usually termed gray pig iron, to distinguish it from the hard irons, which are lighter in color, even to whiteness. A chemical analysis of a really soft pig iron should exhibit about the following percentages of constituent elements:
Graphitic carbon.....3.36 per cent. Silicon.....2.78 per cent. Phosphorus.....0.40 per cent. Manganese.....0.40 per cent. Sulphur.....0.01 per cent. Combined carbon.....0.20 per cent.
Any addition over the quantities given, except for graphite and silicon, would tend to increase the hardness. See GRAY PIG IRON; SOFTENERS.