Iron sponge

Iron sponge is produced commercially, notably in Sweden, whence it was, prior to the Great European War, exported to Germany for use in open-hearth steel manufacture. The process consists in heating iron ore and coal placed in alternate layers in a vessel sealed against the entrance of air. The source of heat is producer gas made from an inferior type of coal, and the vessel is successively heated and cooled for from five to seven days. The maximum temperature attained during the heatings ranges from 1050° to 1200° C. The resulting spongy iron consists of approximately

Iron	96 to 97 %
Sulphur	0.01 to 0.02 %
Phosphorus	0.012 %
Silica	1.4 %

Spongy iron acts as a powerful reducer towards organic matter dissolved in water. In some cases marsh gas is produced. The organic nitrogen is in nearly all cases reduced to nitrogen.