Aluminum complexes molybdates

Other Uses. Photochromic glass contains silver chloride (80) and silver molybdate [13765-74-7] (81) (see Chromogenic materials). An apparatus coated with silver nitrate has been described for the detection of rain or snow (82). Treatment with silver-thiosulfate complex has been reported as dramatically increasing the post-harvest life of cut carnations (83). Silver sulfate has been used in the electrolytic coloring of aluminum (84). Silver sulfate also imparts a yellowish red color to glass bulbs (85). 

Synthesis of phthalocyanine-2,9,16,23-tetrasulfonic acid aluminum(III) complex 48 (R = -SO3 , M == Al(OH)) 10.73 g (40 mmol) 4-sulfophthalic acid monosodium salt, 1.28 g (24 mmol) ammonium chloride, 24.02 g (400 mmol) urea and 0.185 g (0.15 mmol) ammonium molybdate (all chemicals dried) were intensively mixed and placed in a 250 mL glass vessel under dry inert gas. 2 g (15 mmol) water-free aluminum trichloride (purity 99.99%) was added under inert gas. The mixture was heated at first at 140 °C and then within 30 min with stirring to 190 °C, followed by heating at 210 °C for 24 h under inert gas. The blue-colored reaction product was pulverized, treated for 24 h with 1 M aqueous... 

Suarez et al. (36) use a combination of FTIR spectroscopy, electrophoretic mobility and pH titration data to deduce the specific nature of anionic surface species sorbed to aluminum and silicon oxide minerals. Phosphate, carbonate, borate, selenate, selenite and molybdate data are reviewed and new data on arsenate and arsenite sorption are presented. In all cases the surface species formed are inner-sphere complexes, both monodentate and bidentate. Two step kinetics is typical with monodentate species forming during the initial, rapid sorption step. Subsequent slow sorption is presumed due to the formation of a bidentate surface complex, or in some cases to diffusion controlled sorption to internal sites on poorly crystalline solids. 

Identification of the specific species of the adsorbed oxyanion as well as mode of bonding to the oxide surface is often possible using a combination of Fourier Transform Infrared (FTIR) spectroscopy, electrophoretic mobility (EM) and sorption-proton balance data. This information is required for selection of realistic surface species when using surface complexation models and prediction of oxyanion transport. Earlier, limited IR research on surface speciation was conducted under dry conditions, thus results may not correspond to those for natural systems where surface species may be hydrated. In this study we review adsorbed phosphate, carbonate, borate, selenate, selenite, and molybdate species on aluminum and iron oxides using FTIR spectroscopy in both Attenuated Total Reflectance (ATR) and Diffuse Reflectance Infrared Fourier Transform (DRIFT) modes. We present new FTIR, EM, and titration information on adsorbed arsenate and arsenite. Using these techniques we... 

Silicate is determined spectrophotometrically with ammonium molybdate and ammonium vanadate. The pH of the sample must be adjusted to 7-8. Potassium cyanide is added to prevent interference of heavy metals. Oxalic acid is added to destroy mo-lybdophosphate and vanadophosphate and to bind aluminum in a complex. As in all spectrophotometric determinations, high and variable optical absorption of the sample (due to color or turbidity) at the wavelengths of investigation causes errors tannin, iron, and sulfide also interfere. To avoid contamination, all contact surfaces should be of polyethene. It is also possible to determine silicate using FAAS, in which case nitrous acid and ethyne must be used as flame gases. As silicates are present in colloidal form, the sample must be introduced into the AAS equipment using an ultrasonic nebulizer. Such a nebulizer is also used when silicate is measured by ICP-AES. 

Willey (38, 39) has studied the natural interaction of soluble alumina and soluble silica in 0.6 N sodium chloride solution. Addition of aluminum ion to 200 ppm Si(OH)4 retards polymerization. Probably there is formed a colloidal complex which reacts as monomer when put Into the strongly acidic molybdate reagent. A very low concentration of soluble silica also.causes the precipitation of alumina. 

However, when the silica concentration was only 60 ppm, and thus below the solubility of amorphous silica, no polymerization occurs except when alumina is added. In this case when the Al Si ratio is 1 1 to 1 10 the aluminum ion brings together monomer to form a silica-rich complex in which some of the silica is also linked together into a state that is later less molybdate-reactive. Baumann s extensive data deserve detailed study. 

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