Phosphomolybdate

Phosphorus. The presence of phosphorus may be indicated by a smell of phosphine during the sodium fusion. Treat 1 ml. of the fusion solution with 3 ml. of eoneentrated nitric acid and boil for one minute. Cool and add an equal volume of ammonium molybdate reagent. Warm the mixture to 40-50°, and allow to stand. If phosphorus is present, a yellow erystalline precipitate of ammonium phosphomolybdate wUl separate. 

Most of the thiazoles studied absorb in the ultraviolet above 254 nm, and the best detection for these compounds is an ultraviolet lamp (with plates containing a fluorescent indicator). Other indicator systems also exist, among which 5% phosphomolybdic acid in ethanol, diazotized sulfanilic acid or Pauly s reagent (Dragendorff s reagent for arylthiazoles), sulfuric anisaldehyde, and vanillin sulfuric acid followed by Dragendorff s reagent develop alkylthiazoles. Iodine vapor is also a useful wide-spectrum indicator. 

Fig. 4.1 Adsorption isotherms of some organic vapours on ammonium phosphomolybdate outgassed at 180°C. The isotherm temperatures (reading downwards) were 25°C, 25°C, 25°C, 0°C.

Evidence of a different kind is furnished by the fact that the Gurvitsch rule (p. 113) is often obeyed by systems showing Type I isotherms " the amounts of different adsorptives taken up by a given adsorbent, when expressed as a volume of liquid, agree within a few per cent. The order of agreement is illustrated by the typical examples in Table 4.1 for the adsorption of n-alkanes on ammonium phosphomolybdate, and in Table 4.2 which refers to a variety of adsorptives on a silica gel. It must be admitted, however, that there are cases where considerable deviations from the Gurvitsch mle are found, even though the isotherms are of Type 1. Thus, in Table 4.3 the variation in values of the saturation uptake is far outside... 

Fig. 4J1 Adsorption isotherms on ammonium phosphomolybdate powder. (1), (2), before pre-adsorption of nonane (3), (4) after preadsorption of nonane. (1), (4), nitrogen (77 K) (2), (3), carbon tetrachloride (298 K). Adsorption is expressed in mm (liquid).

In a recent paper, Lozano-Calero and colleagues describe a new method for the quantitative analysis of phosphorus in cola beverages. The method is based on the formation of an intensely blue-colored phosphomolybdate complex,... 

The oxidation of methacrolein to methacrylic acid is most often performed over a phosphomolybdic acid-based catalyst, usually with copper, vanadium, and a heavy alkaU metal added. Arsenic and antimony are other common dopants. Conversions of methacrolein range from 85—95%, with selectivities to methacrylic acid of 85—95%. Although numerous catalyst improvements have been reported since the 1980s (120—123), the highest claimed yield of methacryhc acid (86%) is still that described in a 1981 patent to Air Products (124). 

In most analytical procedures for determining the total phosphoms content (normally expressed in terms of P20 ), the phosphates are converted to the orthophosphate form. Typically, condensed phosphates are hydrolyzed to orthophosphate by boiling in dilute mineral acid (0.1 N). The orthophosphate is then deterrnined by gravimetric or spectrophotometric methods. For gravimetric deterrnination, insoluble phosphomolybdates (or magnesium ammonium orthophosphate) is formed. 

According to this mechanism, the reaction rate is proportional to the concentration of hydronium ion and is independent of the associated anion, ie, rate = / [CH3Hg][H3 0 ]. However, the acid anion may play a marked role in hydration rate, eg, phosphomolybdate and phosphotungstate anions exhibit hydration rates two or three times that of sulfate or phosphate (78). Association of the polyacid anion with the propyl carbonium ion is suggested. Protonation of propylene occurs more readily than that of ethylene as a result of the formation of a more stable secondary carbonium ion. Thus higher conversions are achieved in propylene hydration. 

Chemical stabiUty studies are monitored by siUca gel thin-layer chromatography (dc) or by high performance Hquid chromatography (hplc) using a reverse-phase C g coated column (24). Hplc peaks or dc spots are visualized by thek uv absorption at 245 nm the tic spots can also be detected by ceric sulfate or phosphomolybdic acid staining. 

Phosphoms determination involves the conversion of phosphoms to soluble phosphate by digesting the coal ash with a mixture of sulfuric, nitric, and hydrofluoric acids (18). Phosphate is precipitated as ammonium phosphomolybdate, which may be reduced to give a blue solution that is determined colorimetricaHy or volumetricaHy (D2795) (18). 

Phosphomolybdic acid essential oil components stabilization of the silver nitrate-impregnated adsorbent layer [207]... 

Dissolve 250 mg phosphomolybdic acid (molybdatophospho-ric acid) in 50 ml ethanol. 

The phosphomolybdic acid reagent can be employed on silica gel, aluminium oxide, polyamide, RP-2, RP-18 and cellulose phases and also on silver nitrate-impregnated silica gel [13]. 

A solution of phosphomolybdic acid m nitric acid, which gives yellow precipitates of different shades. 

A method that has been the standard of choice for many years is the Lowry procedure. This method uses Cn ions along with Folin-Ciocalteau reagent, a combination of phosphomolybdic and phosphotnngstic acid complexes that react with Cn. Cn is generated from Cn by readily oxidizable protein components, such as cysteine or the phenols and indoles of tyrosine and tryptophan. Although the precise chemistry of the Lowry method remains uncertain, the Cn reaction with the Folin reagent gives intensely colored products measurable spectrophotometrically. 

A. Molybdenum blue method Discussion. Orthophosphate and molybdate ions condense in acidic solution to give molybdophosphoric acid (phosphomolybdic acid), which upon selective reduction (say, with hydrazinium sulphate) produces a blue colour, due to molybdenum blue of uncertain composition. The intensity of the blue colour is proportional to the amount of phosphate initially incorporated in the heteropoly acid. If the acidity at the time of reduction is 0.5M in sulphuric acid and hydrazinium sulphate is the reductant, the resulting blue complex exhibits maximum absorption at 820-830 nm. 

Chloramine-T also functions as a nitrene source in the presence of heteropoly acids (HPAs) such as phosphomolybdic and phosphotungstic acids. The aziridination of alkenes by treatment with the combination of HPA and chloramine-T is... 

See W. F. Giauque and D. P. MacDougall, "Experiments Establishing the Thermodynamic Temperature Scale below 1 =K. The Magnetic and Thermodynamic Properties of Gadolinium Phosphomolybdate as a Function of Field and Temperature". J. Am. Chem. Soc., 60, 376-388 (1938). 

Spray solution 2 Alcoholic phosphomolybdic acid (10 Vo in ethanol). 

In spite of the numerous publications the reaction mechanism is still not finally clarified. A large number of organic compounds can be oxidized by phosphomolybdic acid, with the reduction of some of the Mo to Mo, which then reacts with the re-... 

Note The derivatized steroids can be extracted from the blue chromatogram zones with alcohol and quantitatively determined by means of the Zimmermann reaction, which is not interfered with by the presence of phosphoric acid and phosphomolybdic acid. A yellow background can be bleached by exposure to anunonia vapor [2]. 

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