Amperometric determination of metals forming normal selenites

Summary A new procedure for the quantitative determination of Ag, Hg and Pb has been described. This is based on the precipitation, under appropriate conditions of their normal selenites and titrating amperometrically the excess Se^IV against NaOBr after filtering the precipitate. In this respect the method is almost analogous to the volumetric determination of the above metals after precipitating their pyridine thiocyanate complexes.Sincere thanks of the authors are due to Prof. S. S. Joshi for kind interest in the work, and to the National Institute of Sciences of India for an award of a fellowship to one of them (M. G. B.).     

Liquid chromatographic determination of vanillin and related aromatic compounds

This paper describes a reversed-phase liquid chromatographic method for the determination of vanillin, associated natural aromatic compounds and/or synthetic precursors, ethyl vanillin, and coumarin, a commonly encountered adulterant in nonbeverage and beverage alcohol products using a ternary gradient mobile phase. The compounds were separated on a Nova-Pak C18 column by using water, methanol, and tetrahydrofuran as the mobile phase. Measurements were made by using a photodiode array detector at 275 nm. The choice of the mobile phase and the column provides baseline resolution of vanillin and the associated aromatic compounds commonly found in vanilla-flavoring material. Because this method provides low-level detection/quantitation, it is suitable for the characterization of vanilla flavoring materials that are currently added to vanilla flavored beverage alcohol products.     

Styrene/Methyl Methacrylate-Vinyltns-(methoxyethoxy)silane Copolymers: Synthesis,Characterization, and Thermal Degradation

Vinyltris(methoxyethoxy)silane (VTMES)was copolymerized with methyl methacrylate (MMA) and styrene (St) in bulk at 60°C using benzoyl peroxide as free radical initiator. The copolymer compositions were determined from elemental analysis, and reactivity ratios were calculated by the Kelen-Tüds graphical method. For MMA-VTMES, r₁ = 11.2 ± 0.88 and r₂ = 0 ± 0.16, and for St-VTMES, r₁ = 11.2 ± 2.0 and r₂ = 0 ± 0.34. In both systems r₂ is near zero, indicating that VTMES undergoes little or no polymerization under the experimental conditions. The influence of the silicon comonomer on some of the basic properties of the copolymers (e.g., intrinsic viscosity, solubility, and thermal behavior) was studied.     

Structural and Electronic Properties of Two-Dimensional Materials: A Machine-Learning-Guided Prediction

The growing number of studies and interest in two-dimensional (2D) materials has not yet resulted in a wide range of material applications. This is a result of difficulties in getting the properties, which are often determined through numerical experiments or through first-principles predictions, both of which require lots of time and resources. Here we provide a general machine learning (ML) model that works incredibly well as a predictor for a variety of electronic and structural properties such as band gap, fermi level, work function, total energy and area of unit cell for a wide range of 2D materials derived from the Computational 2D Materials Database (C2DB). Our predicted model for classification of samples works extraordinarily well and gives an accuracy of around 99 %. We are able to successfully decrease the number of studied features by employing a strict permutation-based feature selection method along with the sure independence screening and sparsifying operator (SISSO), which further supports the design recommendations for the identification of novel 2D materials with the desired properties.     

Spectrophotometric determination of uranium(VI) with 1-(2′-thiazolylazo)-2-naphthol in the presence of Trition X-100

Uranium(VI) reacts with 1-(2-thiazolylazo)-2-naphthol to form a red-coloured chelate in the pH range 5.3–7.2, maintained by 0.04 M acetate buffer. Absorbance of the sparingly soluble complex, solubilized and stabilized by Triton X-100, is measured after 30 min and it is stable for at least 16 hours. The complex exhibits maximum absorbance at 575 and 625–630 nm, but absorbance at longer wavelengths is not stable. The 12 complex obeys Beer's law over the concentration range 0.4–6.4 g of uranium(VI) per cm³, has molar absorptivity 3.36·10⁴ dm³·mol^–1·cm^–1, Sandell sensitivity 7.0 ng·cm^–2, formation constant (log K) 9.32 and coefficient of variation ±0.77%. Effect of 60 ions has been studied and selectivity improved considerably in presence of CDTA. The method has been applied for determination of uranium content in a rock sample.