Molybdic acid

In the calciaation process, a mixture of corresponding oxides and an optional modifier, eg, molybdic acid, are milled together to achieve a homogenous mixture. The mixture is calciaed at 750—950°C and milled to a desired particle size. Wet milling ia an alkaline medium is recommended to remove any unreacted vanadium salts that ate beheved to degrade the pigmentary properties of bismuth vanadate (39). 

Molybdfln-saure, /. molybdic acid, -stahl, m. molybdenum steel. 

Recently, a direct synthesis of substituted isoindolinediimines starting from substituted derivatives of phthalic anhydride was reported. The respective derivative of phthalic anhydride was treated with urea and ammonium nitrate in the presence of molybdic acid to give the respective isoindolinediimine.123... 

Absorbance detectors are also commonly used in combination with postcolumn reactors. Here, most issues of detector linearity and detection limit have to do with optimization of the performance of the reactor. In a typical application, organophosphorus compounds with weak optical absorbances have been separated, photolyzed to orthophosphate, and reacted with molybdic acid, with measurement being performed by optical absorbance.58... 

Carl Wilhelm Scheele (1742-1786) isolated "molybdic acid". 

Furthermore, the same sol-gel matrices have been used in a system where acid and base catalysis occur in the same pot without quenching either catalyst [29]. In this case, the acids were either entrapped Nafion (perfluorinated resin sulfonic super acid, a3) or entrapped molybdic acid (M03-Si02, a2), while the bases were two ORMOSILs (organically modified silica sol-gel materials), one with H2N (CH2)2NH(CH2)3 groups (bi) and the other guanidine base residues (b2) (Scheme 5.12). 

Co-extraction of Mo and Cu is potentially a problem with certain feed solutions,14 and again selectivities are very dependent on the nature of modifiers present in formulated reagents.142 The Mo species extracted have not been fully characterized, but may include a neutral dioxo complex, [Mo02L2], which can be assumed to have an N2022 donor set similar to that in the Cu11 complex, and molybdate complexes solvated by neutral phenolic oxime ligands such as [M0O4112 LI l].143 Formation of solvated forms of molybdic acid is supported by evidence that extraction is favorable at very low pH values and that the complexes are readily stripped by aqueous ammonia to produce ammonium molybdate,144... 

J. S. Yadav, S. Raghavendra, M. Satyanarayana, and E. Balanarsaiah, Phospho-molybdic acid supported on silica gel An efficient, mild and reusable catalyst for the chemoselective hydrolysis of acetonides, Synlett, 16 (2005) 2461-2464. 

Gulina, L. B. Tolstoi, V. P. 2004. Synthesis on silica surface by the ionic deposition technique of nanolayers of heteropolycompounds on the basis of phospho-molybdic acid. Russ. J. Gen. Chem. 74 327-330. 

To indicate six-coordination the neutral monomeric molybdic acid is sometimes formulated as Mo(OH)6, but the alternative formulations Mo02(OH)2(H20)2 or Mo03(H20)3 are most likely closer to the truth (58-60) the latter formulation is used in this chapter. An interesting linear relationship has been found (61) between values of the known first protonation constants of the oxoanions of groups 5, 6, and 7 and... 

It has also been reported that D-galactose can be isomerized with molybdic acid to a mixture containing D-talose and D-gulose, but the yields are low.34-35 A number of derivatives of gulono-1,4-lactone have been prepared that, by reduction, would provide selectively protected derivatives of gulose. These derivatives will be discussed in subsequent Sections of this article. 

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. 

Normal isopoly- and peroxymolydates of ammonium and several metals are known. The normal or orthomolybdates may be considered as salts of molybdic acid having formulas H2Mo04 xH20 or M20 Mo03 xH20. They are either of monoclinic or scheelite type crystal structure and obtained as hydrated salts. 

Synonyms molybdenum trioxide molybdic acid anhydride molybdic anhydride molybdic oxide... 

---