Aluminum molybdate, method

By far the most successful method of preparation was via an amorphous organic precursor to the required mixed molybdates, following the method of Delmon et al.(jrT). The method has proved successful for the pure iron, chromium and aluminum molybdates, and also for the mixed phases. A detailed outline of the method taking the example of FeCr(Mo0i )3 is as follows ... 

Soluble silica as determined by the molybdate method is not necessarily present as Si(OH)4. Bogdanova (40) reported that in natural waters that contained only about 5 ppm total silica, 4-9% of the silica was polymeric but was converted to monomer by acid. It is most likely that the polymeric" silica was actually very small colloidal particles of aluminum silicate that liberated monomer when acidified.. ... 

The molybdate method has also been applied for remote determination of silica in highly radioactive defense waste salt solutions of the Savannah River Site (SRS), which suffered the problems with sodium aluminum silicate scale forming in the evaporators used to remove excess process water from the high-level radioactive waste tank farm [4]. 

The molybdate method has been validated by stud)dng the interference effects of several ions by using SnCU, SnCl2, and CeHgOe in HCIO4 as the reducing media in water samples [11]. It was found that the blue silicomolybdate solution is stable for at least 24 h. The blue color conforms to Beer s law for solutions up to 0.09 x 10 M in Si. Aluminum does not interfere up to 0.15 M and Fe + can be determined up to 0.0024 M. SOI", AsO ", PO4", and Cl can be present in limited concentrations NO must be avoided. 

Hexacarbonylmolybdenum was synthesized in low yields by L. Mond by the reaction of pyrophoric molybdenum with carbon monoxide. Presently, it is prepared by carbonylation of M0CI5, molybdic acid, molybdenum sulfide, and other molybdenum compounds. The following reducing agents may be employed Mg, Al, Na, Zn, Fe, Grignard reagents, aluminum organometallic compounds, etc. Sometimes such syntheses involve dry methods whereby no solvent is used. However, most commonly. 

Instead of an alkaline solution, a dilute solution of NaF and HCl to generate HF was employed by Goto (216a) to measure the specific surface area of colloidal silica from the rate of dissolution in this acid medium. The samples from the reaction mi.x-ture were removed, the reaction was stopped by adding aluminum salt to combine with the fluoride, and the dissolved silica was then determined by the molybdic acid method. 

US EPA Method 326.0 allows the combination of suppressed conductivity detection and postcolumn derivatization for UV absorbance detection, as schematically depicted in Figure 8.45. A volume of sample (225 pL) is introduced into an ion chromatography system. After separation and eluent suppression, standard anions and oxyhalide ions are measured using conductivity detection. The suppressed effluent from the conductivity detector is then combined with an acidic solution of potassium iodide (0.26 mol/L) containing a catalytic amoimt of ammonium molybdate tetrahydrate (43 pmol/L). The mixture is heated in the knitted reaction coil to 80 °C to facilitate complete reaction. The formed triiodide is measured by its UV absorption at 352 nm. Because KI is photosensitive, the KI/Mo PCR solution develops a light yellow color with time, even when stored under helium. Therefore, the PCR reservoir has to be protected from light by covering it with aluminum foil and should be pressimzed with helium. Under... 

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