NITROGEN.
The real influence of nitrogen is not known to the author. Percy shows that nitrogenized iron is hard, exceedingly friable, and causes a brilliant, brassy lustre. He also says nitrogen is driven out at a yellow heat; doubtless this is true of the excess of nitrogen, but it has been shown in [Chapter II] that melting in a crucible will not drive the nitrogen out of Bessemer steel.
When crucible-steel not made from Bessemer scrap and Bessemer steel of equal analysis are compared in the tempered condition, there is almost invariably a yellowish tinge over the fresh Bessemer fracture which distinguishes it from the crucible-steel. The Bessemer steel is also the weaker. These differences are believed to be due to nitrogen.
Langley maintains his belief that oxygen is still the chief mischief-maker; the author believes nitrogen to be the more potent of the two; there is no known way to remove the nitrogen, and there the question stands.