Ammonium molybdates complex

The silicic acid concentrations were analyzed at different times by withdrawing 1 ml. from the solution after a high speed centrifugation of the suspended particulates. The colorimetric determination of oligomeric silicic acid by means of the blue ammonium molybdate complex, as described by Stegemann and Fitzek (16), was used for the quantitative measurements. 

Phosphate. Phosphoms occurs in water primarily as a result of natural weathering, municipal sewage, and agricultural mnoff The most common form in water is the phosphate ion. A sample containing phosphate can react with ammonium molybdate to form molybdophosphoric acid (H2P(Mo202q)4). This compound is reduced with stannous chloride in sulfuric acid to form a colored molybdenum-blue complex, which can be measured colorimetrically. SiUca and arsenic are the chief interferences. 

Molybdenum blue method. When arsenic, as arsenate, is treated with ammonium molybdate solution and the resulting heteropolymolybdoarsenate (arseno-molybdate) is reduced with hydrazinium sulphate or with tin(II) chloride, a blue soluble complex molybdenum blue is formed. The constitution is uncertain, but it is evident that the molybdenum is present in a lower oxidation state. The stable blue colour has a maximum absorption at about 840 nm and shows no appreciable change in 24 hours. Various techniques for carrying out the determination are available, but only one can be given here. Phosphate reacts in the same manner as arsenate (and with about the same sensitivity) and must be absent. 

B. Phosphovanadomolybdate method Discussion. This second method is considered to be slightly less sensitive than the previous molybdenum blue method, but it has been particularly useful for phosphorus determinations carried out by means of the Schoniger oxygen flask method (Section 3.31). The phosphovanadomolybdate complex formed between the phosphate, ammonium vanadate, and ammonium molybdate is bright yellow in colour and its absorbance can be measured between 460 and 480 nm. 

Ammonium ions, tetradecyldimethylbenzyl-liquid—Liquid extraction, 1, 548 Ammonium molybdate, 3,1257 Ammonium nitrate, hydroxyl-as plutonium(IV) reductant Purex process, 6, 949 Amphotericin B metal complexes, 2, 973 a-Amylase zinc, 6, 607 Anabaena spp. 

There also exists interference from diphosphoric acid, other more highly condensed phosphoric acids, and their organic derivatives. The free phosphoric acid can be determined as a heteropolyacid complex of phosphoric acid and ammonium molybdate. Afterward the complex is reduced by stannum II chloride to molybdenum blue. The amount of this dye can be measured photometricly at 625 nm. Organic derivatives of phosphoric acid and condensed phosphoric acids do not interfere with this method. 

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... 

Because the preceding chromogenic assay rely on choline quantitation, the hydrolysis of substrates with headgroups other than choline cannot be followed. To circumvent this problem, another useful protocol was devised whereby the phosphorylated headgroup produced by the PLCBc hydrolysis is treated with APase, and the inorganic phosphate (Pi) that is thus generated is quantitated by the formation of a blue complex with ammonium molybdate/ascorbic acid 5 nmol of phosphate may be easily detected. This assay, which may also be performed in a 96-well format, has been utilized to determine the kinetic parameters for the hydrolysis of a number of substrates by PLCBc [37,38]. 

Olsen et al. [62] have described a method for the determination of pH8.5 sodium bicarbonate extractable phosphorus in soils. The concentration of the blue complex produced by the reduction, with ascorbic acid, of the phosphomolybdate formed when acid ammonium molybdate reacts with phosphate is measured spectrophotometrically at 880 nm [63]. 

The limit test for phosphate is based upon the formation of ayellow colour reaction with molybdovanadic reagent (combination of ammonium vanadate and ammonium molybdate) in an acidic medium. However, the exact composition of the molybdovanadophosphoric acid complex is yet to be established. 

The optical activity of the hexitols is of a low order. It may be enhanced by the addition of various complex-forming salts, borax and ammonium molybdate being the ones most used. Since the amount of enhancement is a function of the relative proportions of polyol and booster, it is regrettable that definite amounts of borax or molybdate have not always been reported in the past. 

The optical rotation of aqueous solutions will increase to + 4.0 to +7.0° by the addition of complexing salts, such as borax or ammonium molybdate. 

The template synthesis of phthalocyanine complexes [ZnL] by the condensation of dicyano compounds with urea in the presence of zinc chloride and ammonium molybdate has been described.1136,1137... 

Despite the expenditure of a tremendous amount of effort throughout the world, the two original methods employed in the manufacture of copper phthalocyanine are still used. In the first, a mixture of phthalic anhydride, urea and copper(I) chloride is heated in a high-boiling solvent such as nitrobenzene or trichlorobenzene in the presence of a catalytic amount of ammonium molybdate. The crude copper phthalocyanine is filtered off and the solvent recovered by distillation. The urea acts as a source of nitrogen and the first step in the overall reaction (equation 18) is conversion of phthalic anhydride to phthalimide (219) by ammonia liberated by the urea. More ammonia then converts the phthalimide to l-keto-3-iminoisoindoline (220) and finally to l-amino-3-iminoisoin-dolenine (221). All three intermediates have been isolated and identified. In the presence of copper chloride the l-amino-3-iminoisoindolenine undergoes conversion to the copper complex of phthalocyanine. 

Other molybdenum complexes able to catalyze the selective oxidation of secondary alcohols are ammonium molybdate in the presence of H202,30 benzyltrimethylammonium tetrabromooxomolybdate in the presence of r-BuOOH31 and molybdenum hexacarbonyl in the presence of catalytic cetylpyridinium chloride and stoichiometric t-BuOOH.32... 

Phosphate reacts with ammonium molybdate too, similarly forming yellow phosphomolybdic acid. The presence of phosphate, therefore, interferes in the test. The addition of oxalic acid or citric acid destroys phosphomolybdic acid complex but not silicomolybdic acid complex. The intensity of color developed is proportional to the concentration of sihca in the sample. 

Certain forms of silica and many polymeric silicates do not react with ammonium molybdate. These complex silicates may be decomposed to simple molybdate-reactive silica by high temperature digestion or fusion with sodium bicarbonate. 

The tetrasulfo-Pc complexes of a number of metals are made by the urea melt process by heating the powdered metal, or its acetate, with triammonium-4-sulfophthalate, urea, boric acid, and ammonium molybdate. The metals or metal compounds used are those of chromium (III), manganese(II), iron(II), iron(III), cobalt(II), and zinc(II). Selected synthetic examples of sulfo- and other derivatives of metal phthalocyanines are presented below. 

Molybdate diluting solution. Dissolve 0.5 g of Na2C03 and 0.5 g of Na2B407 in 100 ml of 0.39 M nitric acid. Add 100 ml of molybdate complexing solution and dilute to 500 ml with 0.126 M HN03. This solution can be used until a scale of hydrated molybdenum oxide develops on the container walls (several days to a week). Then a fresh solution should be prepared. The scale can be removed with ammonium hydroxide solution. 

Ammonium molybdate-benzidine test (DANGER THE REAGENT IS CARCINOGENIC.) Silicates react with molybdates in acid solution to form the complex silicomolybdic acid H4[SiMo12O40]. The ammonium salt, unlike the analogous phosphoric acid and arsenic acid compounds, is soluble in water and acids to give a yellow solution. The test depends upon the reaction between silicomolybdic acid and benzidine in acetic acid solution whereby molybdenum blue and a blue quinonoid oxidation compound of benzidine are produced. 

Arsenates and silicates with ammonium molybdate yield the ammonium salts of arsenomolybdic, H3[AsMo12O40] or H3[As(Mo3O10)4], and silico-molybdic, H4[SiMo12O40] or H4[Si(Mo3O10)4], acids respectively these complex acids and their salts react similarly with benzidine. However, phosphates may be detected in the presence of arsenates and silicates by preventing the formation of the corresponding molybdo-acids by the use of a tartaric acid-ammonium molybdate reagent which does not react with arsenic and silicic acids but does react with phosphoric acid when the reaction is carried out on filter paper. 

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