SEVERAL methods of carburizing are unisersally employed in modern engineering practice. For instance, in the pack method usually referred to as “box carburizing” the work is heated in contact with solid compound which, when at temperature, forms carbon monoxide and at the surface of the steel decomposition takes place, nascent carbon going into solution with the steel, and the resultant carbon dioxide reacts immediately with the carbon in the compound to form fresh carbon monoxide. Likewise, liquid carburizing and cyaniding are processes used to accomplish a hard surface with a tougher interior but are limited commercially to a comparatively smaller depth of case than is practised in the pack method.