The ‘easily reducible’ manganese of soils

1. In studying the factors influencing the ‘easily reducible’ manganese in soils, results were obtained to indicate that the estimation is dependent on the pH of the system, the nature of the salt solution, the nature of the reducing agent and the time of contact, in addition to the amount and nature of the higher oxides of manganese present. 2. Pyrolusite (MnO2) and a synthetic preparation of manganite hydroxide are ‘easily reducible’ oxides, while manganite (MnO(OH)) and naturally occurring hausmannite (Mn Mn2O4) are apparently ‘difficultly reducible’ forms. 3. Since pyrolusite occurs in the easily reducible fraction, those deficient soils which contain only a small proportion of their manganese in the easily reducible form must contain the larger part in a form less reactive than pyrolusite.