The monohydrate is a yellow solid consisting of monoclinic crystals; density 3.124 g/cm3 at 15°C; loses water of crystallization on heating at 70°C;
sparingly soluble in cold water (1.33 g/L at 18°C); moderately soluble in hot water 25.68 g/L at 70°C; soluble in caustic soda and sodium carbonate solution. The anhydrous acid consists of white hexagonal crystals; density 3.112 g/cm3; converts to molybdenum trioxide, MoO3 at 70°C; slightly soluble in water; soluble in alkalies and sulfuric acid.
The monohydrate is prepared by treating a molybdate solution with nitric acid, followed by crystallization which may take several weeks to separate out as a yellow solid. The anhydrous molybdic acid is obtained as a white crystalline substance by careful dehydration of the yellow monohydrate.
white crystals or crystalline powder
Molybdic acid is used as a precursor in the production of ammonium molybdate tetrahydrate and molybdenum(IV) sulfide. The mixture of molybdic acid in concentrated sulfuric acid is called as Froehde reagent, which finds application in analytical chemistry for the detection of alkaloids.
Determination of phosphates.
Molybdic acid of commerce iseither ammonium molybdate (molybdic acid 85%)or molybdenum trioxide. The use of the term inter-changeably for these compounds has caused con-fusion. Solutions of molybdic acid are very com-plex chemically since they show a great tendencyto polymerize.
