A new method for determining ferrous iron in paddy soils

Introduction

To make clear the chemical behavior of free iron compounds in paddy soils, it is necessary to find an accurate and rapid method for determining ferrous iron in waterlogged paddy soils. Several methods^1,2,3) have been proposed for this purpose, most of which use dilute acids, such as sulfuric and hydrochloric acid, as extracting reagents. According to the writers' experience, however, these methods seem to be inadequate. The reason is that the acid solutions extract not only ferrous iron, but also ferric iron and reducing substances from soils, and the latter two react immediately in the extract to produce ferrous iron, thus we obtain larger value for ferrous iron than the one actually existing in soils. The writers have found that acetate buffer of pH 2.8 is a very suitable extractant for ferrous iron, and they have been able to establish a new method for the determination of ferrous iron in soils using this buffer. The experimental details will be given in this paper.