Department of Botany, Lucknow University, Lucknow, U. P.
In the determination of total molybdenum in soil, dissolution of the sodium carbonate-soil melt in 6N HCl is preferable to its disintegration in water as it avoids loss of molybdenum and is comparatively more rapid; but the acid dissolution brings large amount of iron in solution which has to be suitably removed. The relative efficiency of the known methods of freeing molybdenum from iron and extracting the former without involving its loss has been tested. Repeated trials, including recovery of molybdenum added to soil before and after fusion with sodium carbonate showed the efficiency of the methods in the order:
Removal of iron by precipitation with NaOH > extraction of molybdenum by complexing it with thiocyanate > removal of iron by precipitation with NHiOH > extraction of molybdenum by complexing with diihiol.
In soils very low in molybdenum, removal of iron by precipitation with caustic soda and its subsequent estimation by the bioassay method using Aspergillus niger has definite advantages over the other procedures.
Determination of total moldbdenum, soils
