Aqueous layer spectroscopy

The extraction procedure of silicate species from the aqueous solutions was explained earlier [7]. An amount of 5 ml of solution was quickly poured into 15 ml of a stirred 0.5 N HC1 solution. An amount of 20 ml tetrahydrofuran (THF) was added and stirring continued for 30 min. Addition of 10.7 g NaCl resulted in a phase separation. The THF layer containing the silicate species was separated from the aqueous layer. The extraction with THF of the aqueous layer was repeated and the THF solutions combined to maximize extraction efficiency. Finally THF was evaporated in a rotavap at 20°C. The final products from the concentrated solutions were gel like. The extracts from the diluted systems were powdery. The experimental details on the gel permeation chromatography (GPC) and IR spectroscopy can be found in refs. [2] and [3], respectively. 

Separate the organic and aqueous layers. Wash the organic layer with H20 (10 mL) and with brine (10 mL). Dry over MgS04, and concentrate under reduced pressure. Distill the residual liquid and collect the colourless liquid boiling at 91 °C at 15 mmHg (1 g, 90%). Characterize the product by 4H NMR, 13C NMR, IR spectroscopy, and high-resolution mass spectrometry. 

Polycrystalline thin films of CdSe have been prepared at the organic-water interface by reacting cadmium cupferronate in the toluene layer with dimethylselenourea in the aqueous layer.31 XRD measurements confirm the formation of cubic CdSe at the interface. TEM images reveal the films to be made up of nanocrystals with diameters ranging from 8 to 20 nm (Figure 10a). Time-dependent growth of the CdSe film at 20 °C has been examined by UV-vis absorption spectroscopy. All... 

The successful identification of cysteine adducts encouraged us to study the reaction of 170 and GSH-cat Fe(III). After careful isolation, an adduct 174, similar to 167, was obtained in 1% yield from the aqueous layer, which was easily rearranged to compound 175 in acidic medium. Thereafter, a similar adduct 176 between GSH and the primary C-radical derived from qinghaosu was isolated and structurally confirmed by NMR and other spectroscopy (Stmcture 5-26). ... 

The reaction mixture is poured into a suitable number of separatory funnels containing a total of 6800 ml. of 12% sulfuric acid and 3000 ml. of petroleum ether. After stirring, the layers are separated. The blue aqueous layer is treated with aqueous 5% sodium thiosulfate until colorless and extracted with petroleum ether. The combined petroleum ether extracts are washed repeatedly with water until neutral and dried over Drierite. After filtering, the petroleum ether is evaporated on a rotary evaporator and the mixture is dried at 80° (2 mm.). The dried residue is 600g. or 2.8 moles (96%) of brown-orange l,l -dimethylferrocene, m.p. 38°. The product may be identified or analyzed for purity by gas chromatography, mass spectrometry, and infrared spectroscopy. 

The solvent index is arranged according to single solvents, nonaqueous-aqueous mixtures and nonaqueous-nonaqueous mixtm-es. Individual solvent systems are indexed accordii to solubilities, pKsp, emf, potentiometric titrations, vapor pressure, cryoscopy, heats of solution, polarography, ligand exchange rates, electrode reactions, electrical double layer, spectroscopy, and organic electrolyte batteries. 

A very similar effect of the surface concentration on the conformation of adsorbed macromolecules was observed by Cohen Stuart et al. [25] who studied the diffusion of the polystyrene latex particles in aqueous solutions of PEO by photon-correlation spectroscopy. The thickness of the hydrodynamic layer 8 (nm) calculated from the loss of the particle diffusivity was low at low coverage but showed a steep increase as the adsorbed amount exceeded a certain threshold. Concretely, 8 increased from 40 to 170 nm when the surface concentration of PEO rose from 1.0 to 1.5 mg/m2. This character of the dependence is consistent with the calculations made by the authors [25] according to the theory developed by Scheutjens and Fleer [10,12] which predicts a similar variation of the hydrodynamic layer thickness of adsorbed polymer with coverage. The dominant contribution to this thickness comes from long tails which extend far into the solution. 

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