Spectrophotometric determination of trace amounts of selenium with catalytic reduction of bromate by hydrazine in hydrochloric acid media

A method is presented for the determination of selenium, based on the catalytic effect of selenium(IV) on the reduction reaction of BrO(-)(3) by N(2)H(4).2HCl. The decolourization of Methyl Orange by the reaction products was used to monitor the reaction spectrophotometrically at 525 nm. This method is precise, highly sensitive, simple, rapid, widely applicable and selective for the determination of selenium(IV) and total selenium. The variables which affected the reaction rate were fully investigated and the optimum conditions were established. Selenium, as low as 1 ng/ml, can be determined by this method. The relative standard deviation of 20 ng of selenium was 0.94% (N = 10). The method was applied to the determination of Se(IV) in a health-care product.     

Complex formation of gallium(III) with 8-hydroxy-7-iodoquinoline-5-sulphonic acid (ferron)

The complex formation of gallium(III) with 8-hydroxy-7-iodoquinoline-5-sulphonic acid (ferron) (L) was studied by potentiometry; and the dissociation constants of the ligand were redetermined. A new computer program made it possible to make allowance for a considerable number of equilibria. In the pH range 2–10, the main species were as follows (the logarithm of the absolute stability constants at 25.0 ±0.1° for ionic strength 0.1 M are given in parentheses): GaHL (11.3), GaL (14.7), Ga(OH)₂L (32.3), GaL₂ (23.9), GaOHL₂ (31.0) and GaL₃ (29.6). For 1:1, 1:2 and 1:3 mixtures of metal with ferron, the mole fractions of the various complexes as a function of pH were calculated; the effect of pH on the conditional constants of the species GaL, GaL₂ and GaL₃ was also established.     

Static bending of granular beam: exact discrete and nonlocal solutions

Meccanica - This study is an attempt towards a better understanding of the length scale effects on the bending response of the granular beams. To this aim, a unidimensional discrete granular chain...     

Spectrophotometric solvent extraction studies of 2-mercaptopyridine-1-oxide and uranyl ion complex

The complex formed by uranyl ion with 2-mercaptopyridine-1-oxide (thione) is studied by spectrophotometry. At pH 4.5 and 25 degrees the only complex formed is UO(2)(thione)(3)(-). The conditional stability constant of this complex is 2.6 x 10(12). Tributyl phosphate is used for the extraction of the complex from the aqueous phase and the extraction constant is 8.9 x 10(12). The use of the reagent for the separation and determination of uranyl ion is elaborated.     

Some observations on the solvent extraction and spectrophotometric determination of palladium using 3,4-dihydro-4,4,6-trimethyl-2(1H)-pyrimidine-thione as a selective reagent

A highly selective spectrophotometric method is described for the determination of palladium, using 3,4-dihydro-4,4,6-trimethyl-2(1H)-pyridinethione (DTPT). The intense yellow 1:2 complex is extractable in chloroform from aqueous solution of pH 5.5. The maximum absorption occurs at 420 nm, ε = 3.90 × 10⁴ liter/mol⁻¹ cm⁻¹ and the sensitivity of the determination is 0.023 μg/ml. Palladium can be determined over a range of 0.4–24.6 ppm. CN⁻ interferes in this determination and should be absent. The method is applied to the determination of palladium in hydrogenation catalysts.     

Composite of conducting polyaniline-isobutylated urea formaldehyde: Preparation and characterization

Composite of conductive polyaniline-isobutylated urea formaldehyde have been prepared by chemical oxidative emulsion polymerization of aniline in the presence of isobutylated urea formaldehyde resin (BUFR) in toluene-water solvents at room temperature. The mass loading of polyaniline was controlled by varying the BUFR/aniline charging ratio as well as oxidant (ammonium persulfate)/aniline molar ratio. Some factors capable of affecting the yield and conductivity of composite, such as amount of the oxidant, type of the dispersants (span-80 and span-20), and amount of resin and organic acid (para-toluene sulfonic acid) were investigated. The prepared composites were characterized by FTIR spectroscopy and scanning electron microscopy (SEM).