Contributions to the basic problems of complexometry-XXVII. Influence of magnesium on masking of calcium with fluoride in the determination of manganese

Determination of manganese in the presence of calcium and magnesium after their masking with ammonium fluoride was reinvestigated. Normally such a determination gives low results caused by co-precipitation of manganese with calcium fluoride. It has been found that the co-precipitation is highest when magnesium is absent in the solution. With increasing concentration of magnesium ions co-precipitation of manganese decreases and at the ratio ca:Mg = 0.5-1 is entirely eliminated. An explanation of this phenomenon is discussed.