Description
Phosphomolybdic acid (H5Mo12O41P) is classified as a reagent and an indicator, specialty chemicals. These are substances which are used for the identification, detection and analysis of pathologic, biological or chemical conditions or processes. Indicators such as Phosphomolybdic acid undergo changes in their physical appearance, such as color changes, when a certain chemical titration is approaching the endpoint, for instance, the transition between acidity and alkalinity. On the other hand, a reagent is used to determine or detect the presence of another substance microscopically or chemically, especially through analysis. Reagents may also include colourimetric reagents, fluxes, reducers, oxidizers, solvents and precipitants.
Chemical and Physical properties
Phosphomolybdic acid has a molecular weight of 1843.373 g/mol, a monoisotopic mass of 1866.669 g/mol and an exact mass of 1841.674 g/mol. It has a hydrogen bond donor and acceptor count of 4 and 41 respectively. Phosphomolybdic acid has a heavy atom count of 54 and a complexity of 112. It has a topographical surface area of 693 A^2 and a covalently-bonded unit count of 14.
Preparation
Phosphomolybdic acid catalysts can be prepared by forming a mixture of hydrated Phosphomolybdic acid in an anhydrous alkyl alcohol. This is followed by adding a base to the mixture and evaporating the mixture to form a catalyst powder, and subsequently calcining and dehydrating the powder to yield the active catalyst. The second method of preparation entails the formation of a solution containing hydrated Phosphomolybdic acid in an anhydrous alkyl alcohol, evaporating the mixture to yield a concentrate and adding a catalyst support substance with the concentrate. This step is followed by contacting the impregnated support with gaseous ammonia in amounts that can yield an insoluble precipitate for ammonium alkyl Phosphomolybdic acid within the membrane of the support substance and thereafter dehydrating and calcining the support material to yield the coated catalyst.
A phosphomolybdic acid stain is prepared by dissolving 10g of phosphomolybdic acid in 100ml of absolute ethanol.
Applications
A phosphomolybdic acid solution is a multipurpose staining reagent that is applied in chromatography and other uses available in concentrations of 10-20% in polar organic solvents such as ethanol. Phosphomolybdic acid is a quality universal stain which is mildly sensitive to solutions with low concentrations. It stains a majority of functional groups, but it fails to highlight various groups on the basis of the staining spots indicated on the TLC plate. TLC’s treated with Phosphomolybdic acid are indicated with a light green colouration, whereas compounds of interest are highlighted by relatively dark green spots. It is essential to apply heat treatment to TLC plates with the Phosphomolybdic acid solution to activate the stain for visualization. Phosphomolybdic acid stains have a relatively long shelf-life, on condition that solvent evaporation is minimal.
The Phosphomolybdic acid may also be used as a reagent for alkaloids and as an additive in plating processes. It may also be used in enhancing water resistance in cement, adhesives and plastics. It may be applied as a laking agent in basic dyes, as a fixing agent in photography and in pigments.
Catalysts comprising various salts and Phosphomolybdic acid are utilized in various sectors of petrochemical processing. It is particularly significant in its application in catalysis during the selective direct oxidation of aldehydes such as methacrolein and isobutyraldehyde to their subsequent dehydrated methacrylic acid and carboxylic acid. Catalysis in the presence or absence of dehydrated Phosphomolybdic acid in combination with trace amounts of promoters such as decomposable salts of alkaline earth metals and alkalis, copper, bismuth, arsenic, antimony, tellurium and hydroxides has gained a lot of economic interests in recent years.
Chemical Properties
yellow crystal(s); oxidizing agent; used as a reagent for alkaloids, as a pigment; imparts water resistance to plastics [HAW93]
Uses
Weighting silks; as reagent for alkaloids, uric acid, xanthine, creatinine, some metals, with hematoxylin as nerve stain in microscopy.
