A STUDY OF THE IRON IN A PODSOL SOIL BY MEANS OF AN IMPROVED DIPYRIDYL METHOD

Abstract
An accurate determination of the ferrous and ferric iron content of a colored soil extract is possible by the direct application of the dipyridyl method when an Evelyn photoelectric colorimeter and a suitable light filter are employed.It is shown that a sodium carbonate treatment of a podsol soil increases the water extractable iron and organic matter. The soluble iron is contained in the humic acid fraction. Since the iron in these extracts reacts quantitatively with αα′-dipyridyl, it is believed to be entirely combined in a manner similar to that of the soluble unionized complexes of iron with hydroxy organic acids.

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