On Easily Soluble (Hydrolyzable) Iron in Soils

Abstract

Iron was extracted from soils by 2% HCl in two ways; one was at room temperature and the other, at 70℃. Fe_2O_3 from the former way was supposed to be mostly from limonite, and that from the latter way, mostly from hematite. As hematite was, in general, less hydrated than limonite, a ratio of Fe_2O_3 of the former to that of the latter (Fe_2O_3,Sol. at 70℃/Fe_2O_3,Sol. at room temp.) was considered to show somewhat the degree of hydration of iron in the soils. From the results of determining this ratio with the soils (see Table 1 and Table 2), it was found that iron was less hydrated in the order : Subsoil of Red soil>Subsoil of Terra rossa>Subsoil of alluvial soil (Gray lowland soil)>Subsoil of volcanic ash soil (Brown forest soil)