Sorption hysteresis on microrough surfaces

Numerical experiments on the adsorption of water vapor based on vapor silver substrates with different microroughness were performed using a modified Langmuir adsorption model. The calculations revealed a number of phenomena making it possible to clarify the interpretation of many experimental data on sorption. It is established that significant initial microroughness of a silver substrate causes a sharp increase in the number of molecules of an equilibrium adsorbate and provides a stable liquid film of the adsorbate under conditions close to saturation conditions. It is shown that stability of the film state is due to the fact that its further growth or evaporation are only possible because of nucleation processes under significant supersaturation or overheating. The results obtained can be used to improve technologies based on adsorption processes.     

Adamantylazoles: IX. Acid-catalyzed Adamantylation of 1,2,4-Triazol-3-thione

1,2,4-Triazole-3-thione reacts with 1-adamantanol in sulfuric acid to form 1-(1-adamantyl)-3- [(1-adamantyl)sulfanyl]-1,2,4-triazole and 3,3′-disulfandiylbis[1-(1-adamantyl)-1,2,4-triazole].__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 1, 2005, pp. 142–145.Original Russian Text Copyright © 2005 by Amandurdyev, Saraev, Polyakova, Golod.     

Separation of water-soluble vitamins on silica modified with L-cysteine–stabilized gold nanoparticles using HPLC

Silica functionalized with 3-aminopropyltriethoxysilane and L-cysteine–stabilized gold nanoparticles has been obtained (SiO₂–NH₂–Au–L-cysteine). The influence of pH and the content of acetonitrile in the mobile phase on retention and separation selectivity of eight vitamins has been studied. The chromatographic conditions that enable the separation of C, B3, B12, B5 and B1, B2, B6, B10 mixtures of vitamins have been proposed. It has been found that it is possible to separate a mixture of vitamins C, B3, B12, and B5 in 8 min, and a mixture of vitamins B1, B2, B6, B10 in 12 min on the synthesized sorbent SiO₂–NH₂–Au–L-cysteine in isocratic elution mode.     

Effect of the conditions of sample preparation for x-ray fluorescence analysis on the effect of microabsorption heterogeneity

The dual effect of the microabsorption heterogeneity (MAH) of emitters on the fluorescence intensity (I _fl) is shown on the basis of the literature data. The duality is due to the covering of large fluorescent grains by small filler particles (II type effect) and its absence (I type effect). For some materials, the effect of MAH can change not only in magnitude but also in sign. It is shown experimentally that the prediction of the covering effect is difficult. It was found that, upon crushing multicomponent materials, different granulometric fractions differ in their chemical composition. This makes the theoretical account of the effect of the MAH of the emitter on the results x-ray fluorescence analysis hardly probable. It is shown that the experimental account by means of radiation scattered (I _σ) or absorbed (I _ab) by the sample possible only in a particular case, because the dependences I _fl,I _σ, and I _ab on the particle size differ in nature.     

Phases containing tungsten in Cu(1) positions

A tetragonal (123) phase of composition CdBa₂Cu₂WO₈ with the complete and selective substitution of tungsten atoms for copper in the Cu(1) positions is synthesized from CdWO₄ and BaCuO₂ at 800°C in flowing oxygen. The percentage of the (123) phase in the sample is at least 90%; the unit cell parameters are a = b = 0.4151(3) nm, c = 1.2537(8) nm. The X-ray diffraction pattern shows a superstructure with all three of the unit cell parameters being doubled.     

ZrO<Subscript>2</Subscript>–Carbon nanotubes composite sorbent for treatment of aqueous solutions to remove boron

A composite adsorbent based on zirconium dioxide hydrosol and functionalized carbon nanotubes for removing soluble boron compounds from aqueous solutions was synthesized by the sol–gel method. Measurements of the borate adsorption on the synthesized adsorbent samples showed that introduction of carbon nanotubes into ZrO₂ sols used for preparing the adsorbents enhanced the adsorption ability of the adsorbents.     

anti-syn and anti-anti coordination of the bridging CO 3 2− group in [Cu2(Phen)4(μ-CO3)]B10H10 binuclear complexes: Synthesis, structure, and magnetic properties

A redox reaction that occurs in the [Cu₂B₁₀H₁₀]/Phen system in CH₃CN/DMSO and CH₃CN/DMF in air yields a Cu(II) binuclear complex, [(Phen)₂Cu(CO₃)Cu(Phen)₂]²⁺. The [Cu₂(Phen)₄(μ-CO₃)]B₁₀H₁₀ · 2.5DMSO · 2H₂O (I) and [Cu₂(Phen)₄(μ-CO₃)]B₁₀H₁₀ · 4DMF (II) compounds have been isolated and studied by X-ray crystallography at 150 K and EPR at 295 K. Their magnetic properties have been studied in the range 300–2 K. In the cations of both compounds, the bridging CO ₃ ^2? group is bidentately coordinated to two Cu atoms. The cations in I and II have different spatial orientations of the Cu-O bonds: anti-syn and anti-anti, respectively. Compound I has weak magnetic interactions caused by a short Cu…Cu distance (4.441 Å) in the dimer. No exchange coupling is observed in II.