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Ohne Zusammenfassung     

Spectrophotometric determination of selenium with dithizone

Microgram amounts of selenium(IV) are determined by measuring the decrease in absorbance of dithizone in carbon tetrachloride solution at 620 nm. Relative standard deviations for samples containing 0.20 and 1.00 μg of selenium(IV) are 0.6% and 0.4%, respectively. Of several metals tested only copper (at the 1.0-μg level) and iron (at the 100-μg level) interfere but high concentrations of nitric or perchloric acid cause low results. A reinvestigation of the reaction of selenium(IV) with dithizone suggests a formula Se(HDz)₄ for the dithizonate.     

The determination of selenium(IV) by thermometric enthalpy titration with thiosulphate

Selenimn(IV) can be titrated in the range 0.2–6 mg with thiosulphate; relative standard deviations are 1.2–0.54%. Experimental conditions were manipulated to use the endothermic enthalpy of dilution and disproportionation of thiosulphate to advantage in improving end-point precision. Common anions do not interfere; interferences from copper(II), iron(III), lead(II) and mercury(II) can be minimized by masking.     

Kristallstrukturen zweier Modifikationen von In5Mo18O28 und deren Zwillingsbildung

Crystal Structures of Two Forms of In₅Mo₁₈O₂₈ and Twinning In₅Mo₁₈O₂₈ is prepared from In, Mo and MoO₂ at 1 150°C in an evacuated quartz glass ampoule. X-ray investigations on single crystals show monoclinic symmetry (a = 1 323.13(9), b = 951.88(10), c = 989.48(8) pm, β = 100.976(4)°, space group P 2₁/c (No. 14)) for form 1 . The second form ( 2 ) crystallizes in the orthorhombic system (space group Pmcn (No. 62), a = 2 596.6(5), b = 952.0(2), c = 989.6(2) pm). Twinning and charge balances are discussed.     

Asymmetric aldol reactions catalyzed by the promiscuous aldo–ketoreductase enzyme

The promiscuous aldo–ketoreductase (AKR) enzyme is used as a sustainable biocatalyst for the first time to catalyze asymmetric aldol reactions in aqueous medium. The reactions between aromatic aldehydes and cyclic/acyclic ketones give the corresponding products in moderate yields and enantioselectivities in the presence of water. The influence of solvents, the mole ratio of substrates, and enzyme concentration are investigated. The mechanism of the AKR1A1-catalyzed aldol reaction is also discussed.     

LDH-intercalated d-gluconate: Generation of a new food additive-inorganic nanohybrid compound

Intercalation of d-gluconate into the interlamellae of zinc-aluminum-layered double hydroxide for the formation of a food additive-inorganic layered nanohybrid was accomplished by both direct (co-precipitation) and indirect (ion-exchange) methods. Powder X-ray diffraction (PXRD) together with CHNS and Fourier transform infrared (FTIR) analyses showed that the hybridization of d-gluconate with pure phase and good crystallinity was successfully accomplished by a direct method within ranges of pH 7.5-10, Zn to Al initial molar ratio of 2-5 and DG concentration of 0.05-0.3 M. The same nanohybrid compound was also prepared using an indirect ion-exchange method by contacting the pre-prepared LDH with 0.1 M DG for 80 min. The basal spacing of the nanohybrid synthesized by the direct method ranged between 9 and 12.0 Å while that synthesized by the indirect ion-exchange method was 14.0 Å. The crystallinity of the latter was higher than the former and it inherited the crystallinity of the precursor. This work shows that a food additive, such as d-gluconate, can be hybridized into an inorganic host for the formation of a new nanohybrid compound, which can be used to regulate the release of acidity in the food industry.     

Self-diffusion of uranium in uranium dicarbide UC2

The self-diffusion of uranium in uranium dicarbide, UC₂, was measured between 1670 and 2500 K using the α-energy degradation method with the thin layer condition and U-233 as tracer. The activation enthalpy was 5.7 ± 0.2 eV. A discontinuity was indicated at ≈ 2050 K, the transition temperature of α-UC₂ to β-UC₂.     

Messung von Intensitätskorrelationsfunktionen bei Laserlicht

Ohne Zusammenfassung