Removal of Manganese Prior to Calcium and Magnesium Precipitations

Abstract

Manganese is a minor constituent of portland cement. Its removal during analysis is frequently required in order to determine the true calcium and magnesium oxide values. Present federal and ASTM specification methods call for removal by bromine in ammoniacal solution, but do not always give consistent or complete removal of the manganese.A method based on oxidation by potassium permanganate in ammoniacal solution was suggested to ASTM Committee C-l and tried in several laboratories.This paper describes modifications of the originally suggested method which were found necessary in order to obtain satisfactory results. The permanganate method described gives better removal than the bromine procedure. No manganese could be detected in calcium precipitates and not over 0.003% MmO; in magnesium precipitates following such removal. The method is shown not to affect results for calcium and magnesium oxides when used in analysis of a high-manganese cement and NBS standard sample IA, argillaceous limestone.

Determinação de cálcio e magnésio pelo EDTA em extratos ácidos de solos

“…É difícil obter a precipitação quantitativa do manganês, utilizando a água de bromo como oxidante (5,8). A má oxidação do manganês pelo bromo pode ser explicada pela reação deste último com o íon amônio, que se processa em meio ligeiramente ácido ou básico, portanto dentro das condições de trabalho:…”

Inorganic Gravimetric and Volumetric Analysis

“…6063 (1954). (57) Kuhn, A., Naturwissenschaften 42, 529 (1955). (58) Lacourt, A,, Heyndrycky, P., A'ature 176, 880 (1955).…”