Determination of water content by means of the Derivatograph

The determination of water content by means of the Derivatograph is treated in the paper. The determination of water in analytical precipitates, various pharmaceutical products, biological substances, the products of food industry is treated on the basis of some practical examples. The applicability of the Derivatograph for determining the adsorption capacity of industrial adsorbents, the hydration conditions of cement, the system Ca₃A-CaSO₄ · H₂O and the rehydrability of clay minerals is demonstrated. The aluminium oxide barrier layers were investigated on the basis of the water content of the aluminium hydroxide. For the characterization of the different strengths by which water is bound in strontium chloride hydrates the apparent activation energies are also presented.     

Investigation of lead thiosulfate photolysis in aqueous solutions

A model of photolysis of PbS₂O₃ aqueous solutions has been proposed on the basis of identified photolysis products and semiempirical quantum-chemical calculations. The degradation of PbS₂O₃ starts with the dissociation of the sulfur-sulfur bond in the thiosulfate group via photochemical excitation and transition of the system a whole to the activated state, which is decomposed by the solvent. The interaction of the primary photolysis products with PbS₂O₃ results in the formation of final products.     

Thermal decomposition products of polypropylene

Isotactic polypropylene was decomposed under vacuum at 360, 380, and 400°C, and the volatile products from C₁ to C₁₂ hydrocarbons were analyzed by gas chromatography. The formation of the main products is discussed on the basis of a free-radical mechanism in which intramolecular radical transfer is assumed to play an important role. The mechanism of the formation of a number of products suggested by previous workers is criticized on the basis of the results of a more comprehensive analysis of this investigation.     

Synthesis and properties of Na6[Pb(S2O3)4] · 6H2O

Conditions for the synthesis of the water-soluble lead thiosulfate complex Na₆[Pb(S₂O₃)₄] · 6H₂O were determined. The complex synthesized was characterized by UV and IR spectroscopy and X-ray phase and thermal analyses. Thermolysis schemes were proposed on the basis of the IR and mass spectra of the thermal decomposition products.     

Mechanism and rate constants for ammonia photochemical oxidation with O2 on the singlet and triplet potential energy surfaces

The mechanism and thermodynamic of NH₃ + O₂ reaction on the singlet and triplet potential energy surfaces (PES), were carried out using the RMP2 and CCSD (T)//RMP2 theoretical approaches in connection with the 6-311++G(d, p) basis set. Three pre-reactive complexes, ¹C1, ¹C2, and ³C1 on the singlet and triplet PES were formed between ammonia and molecular oxygen. With variety of pre-reactive complexes, six types of products are obtained, of which two types are found to be thermodynamically stable. The mechanistic properties of all products channels are discussed. Results show that production of HONO + H₂ and HN(OH)₂ are the main reaction channels in thermodynamic viewpoint with the Gibbs free energy of ?G° = ?34.681 and ?27.153 kcal/mol, respectively. Rate constants of the title reaction over the temperature range of (200–1000 K) show kinetic products are different from thermodynamic products.     

Thermal decomposition products of polyisobutylene

Polyisobutylene was decomposed at 325, 345, and 365°C under vacuum, and the volatile products were trapped by using liquid nitrogen. The products, C₁–C₂₄ hydrocarbons, were analyzed by gas chromatography. The formation of the main products is discussed on the basis of a free-radical mechanism. Intramolecular radical transfer can account for the production of most fragments including dimers, trimers, tetramers, and so on, of isobutylene.     

Analysis of the Fundamental Aspects of Oxidation of Rich Methane Mixtures in Matrix-Type Converters

Equilibrium distribution of oxidation products was calculated for the system СН₄ + ψО₂ → products at 0.5 < ψ < 1.0 and temperature of 900–1700 K, with the existence of phase transitions in the system taken into account. Two regions are conditionally distinguished: I, at ψ > 0.6 and temperatures higher than 1000–1200 K (depending on ψ), when there is no Csolid in the system; and II, if this component is present in the system. The range of working temperatures and values of ψ, at which the matrix conversion process occurs, falls within region I. A nearly 100% conversion of oxygen and methane is reached within this region; there is no Csolid; and CO, H₂, CO₂, and H₂O are products of the partial oxidation of methane in equilibrium. The temperature limits within which the system passes into region II and the formation of the synthesis gas is accompanied by the appearance of soot were determined. Formulas describing the dependence of the yield of oxidation products per mole of converted methane at various ratios between the methane and oxygen concentrations were derived. An expression was obtained on the basis of experimental data, which can be used to approximately calculate to within <6% the most important technological parameter of the matrix conversion process, [H₂]/[CO] ratio.     

Preparation of isomeric 1,3- and 1,5- (o-phenylene)-hexamethylcyclotetrasiloxanes and investigation of their spectral characteristics

Workup of the mixture of products of pyrolysis of cyclotetrasiloxane (Me₂SiO)₂(MePhSiO)₂ yielded 1,3- (I) and 1,5-(o-phenylene)cyclosiloxane (II), the structures of which were established on the basis of data from their IR, PMR, and mass spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 24–25, January, 1978.     

The non-isothermal decomposition of cobalt acetate tetrahydrate

The non-isothermal decomposition of cobalt acetate tetrahydrate was studied up to 500°C by means of TG, DTG, DTA and DSC techniques in different atmospheres of N₂, H₂ and in air. The complete course of the decomposition is described on the basis of six thermal events. Two intermediate compounds (i.e. acetyl cobalt acetate and cobalt acetate hydroxide) were found to participate in the decomposition reaction. IR spectroscopy, mass spectrometry and X-ray diffraction analysis were used to identify the solid products of calcination at different temperatures and in different atmospheres. CoO was identified as the final solid product in N₂, and Co₃O₄ was produced in air. A hydrogen atmosphere, on the other hand, produces cobalt metal. Scanning electron microscopy was used to investigate the solid decomposition products at different stages of the reaction. Identification of the volatile gaseous products (in nitrogen and in oxygen) was performed using gas chromatography. The main products were: acetone, acetic acid, CO₂ and acetaldehyde. The proportions of these products varied with the decomposition temperature and the prevailing atmosphere. Kinetic parameters (e.g.E and lnA) together with thermodynamic functions (e.g. °H, C _p and °S) were calculated for the different decomposition steps. In celebration of the 60^th birthday of Dr. Andrew K. Galwey     

Brown ceramic pigments based on open-hearth slag

The possibility and expediency of the application of dump waste open-hearth slag for obtaining ceramic pigments was revealed on the basis of complex physicochemical studies. Ceramic pigments of a brown color gamma were synthesized in the system open-hearth slag-Cr₂O₃-NiO. The composition of the crystal phase of roasting products of pigment burdens and its correlation with optical color indexes were determined. Laboratory and production tests of developed slag-containing pigments in the composition of various vitreous coatings were carried out.     

Chemical effects induced by γ-irradiated ammonium chloride in aqueous medium

Dissolution of -irradiated ammonium chloride in aqueous solutions of nitrate and iodide results in the formation of NO ₂ ^– and I₂ as products. Appropriate mechanisms have been suggested in the light of known stable radiolytic products formed in the salt during irradiation. The variation in the yields of products in the solution with the variation in -dose, amount, particle size is studied. The effect of thermal annealing on the yields of products is explained on the basis of annealing of radiolytic products.     

Molecular structures of mononitroanilines and their thermal decomposition products

The molecular structures of 2-nitro, 3-nitro, and 4-nitroaniline and their internal rotational isomers were calculated by anab-initio method using HF/6-31G* basis set. The geometries were influenced by the nitro group's position. The perturbation of the amino group on the nitro group was observed in a 2-nitroaniline isomer having a molecular structure distinct from that of the other two isomers. Among them, 4-nitroaniline is the most stable one. Internal rotation tests of either the nitro or amino group of 3-nitro and 4-nitroaniline indicate that no significant deformations of the phenyl ring occurred after internal rotation; however, the internal rotational isomers of 2-nitroaniline differed from its original structure. Relatively easier internal rotation of the nitro group than the amino group and different C-NO₂ and C-NH₂ bonds indicate the bond-breaking message of nitroanilines. As products of explosives induced by thermal or shock are of interest, five products of 2-nitroaniline were selected to assess their geometries and energies. The above calculations revealed that these products are thermodynamically unfavorable.     

Optical Emission Spectroscopic Study of the Synthesis of Titanium Boride Nanoparticles in RF Thermal Plasma Reactor

Thermal plasma processes have been investigated by optical emission spectroscopy during the synthesis of TiB_x nanoparticles from TiO₂, B and C precursors using argon and helium both as plasma and sheath gases. Line-rich emission spectra were observed both in Ar–He–TiO₂–B and Ar–He–TiO₂–B–C cases. Emissions detected in the spectral region of 300–1000 nm were attributed to the electronic relaxation of excited Ti(I) and ionic fragments Ti(II), as well as the molecular species of TiO. The plasma temperature was calculated from the vibration–rotation temperature of the A–X electronic transition of TiO molecule by the least-squares fitting of experimental data to theoretical spectra. The temperatures at 100 mm downstream the torch outlet were found to be between 3800 and 2700 K for the Ar–He–TiO₂–B system, and between 5100 and 4300 K for the Ar–He–TiO₂–B–C system, respectively. The morphology of as-formed nanoparticles was characterized by transmission electron microscopy. Measurements of specific surface area, evaluated on the basis of Brunauer, Emmett and Teller equation, revealed that in all experimental setups titanium boride nanoparticles were formed with a mean particle size of 17–85 nm. On the basis of X-ray diffraction patterns, the solid reaction products were composed of TiB₂, boron doped titanium indicated as Ti(B), Ti₂O₃, H₃BO₃ and TiC. The actual composition of products depended on the synthesis conditions.     

Revelation from the Reaction of 1,4‐Diazabutadiene with Perchloric Acid: An Approach to the Synthesis of Imidazolium Perchlorates

The reactions of 1,4‐diazabutadienes 1 with HClO₄ were studied in detail. The final products obtained were not the hydroperchlorates of 1 but imidazolium perchlorates 2 or 3 . A possible reaction process is postulated on the basis of the isolation of the intermediate 2‐iminomethylimidazolium salt 4 . The factors influencing the conversion of 4 to the imidazolium perchlorates 2 and 3 were discussed with regard to the electronic and steric effects of the N‐substituents. This reaction can serve as an approach for the synthesis of imidazolium derivatives.     

Ground-state dynamics of α-methylstyrene. I. Thermally induced oligomerization in bulk

α-Methylstyrene (α-Me-St) in bulk undergoes a variety of thermally induced processes which we investigated in detail by product-distribution analysis. The oligomeric products, shown by GC–MS coupling techniques and independent syntheses, consisted of nine dimers and nine trimers with no detectable higher oligomers or polymers. Two isomeric cyclobutanes and one of the open-chain unsaturated dimers were formed by a conventional two-step cycloaddition; a Flory-type diradical was the common intermediate. In contrast to these 2π + 2π products, the majority of the remaining oligomers could not be interpreted on the basis of π-electron interaction between closed shell molecules. Their structures, however, were compatible with a free radical process in which cumyl(MH·) and 1,4-dimethyl-1-phenyl-tetrahydronaphthalene-yl(THN·), which are consecutive products of 4π + 2π and 2π + 2π interactions, respectively, were involved in addition and transfer reactions. Because of the small rate of initiation and the obvious lack of free radical recombination products, a mechanism was suggested in which MH· and THN· radicals react predominantly in a closed sequence of elementary processes and to a rather small extent only by bimolecular free radical termination. Two sorts of stabilization steps, hydrogen transfer to monomer (R_nH· + M → R_n + MH·) and hydrogen abstraction from a hypothetical 4π + 2π intermediate I (R_nH· + I → R_nH₂ + THN·), are attributed to the high rates of unsaturated and saturated oligomer formation.     

Simulation of Organic Liquid Product Deoxygenation through Multistage Countercurrent Absorber/Stripping Using CO2 as Solvent with Aspen-HYSYS: Process Modeling and Simulation

In this work, the deoxygenation of organic liquid products (OLP) obtained through the thermal catalytic cracking of palm oil at 450 °C, 1.0 atmosphere, with 10% (wt.) Na₂CO₃ as a catalyst, in multistage countercurrent absorber columns using supercritical carbon dioxide (SC-CO₂) as a solvent, with an Aspen-HYSYS process simulator, was systematically investigated. In a previous study, the thermodynamic data basis and EOS modeling necessary to simulate the deoxygenation of OLP was presented. This work addresses a new flowsheet, consisting of 03 absorber columns, 10 expansions valves, 10 flash drums, 08 heat exchanges, 01 pressure pump, and 02 make-ups of CO₂, aiming to improve the deacidification of OLP. The simulation was performed at 333 K, 140 bar, and (S/F) = 17; 350 K, 140 bar, and (S/F) = 38; 333 K, 140 bar, and (S/F) = 25. The simulation shows that 81.49% of OLP could be recovered and that the concentrations of hydrocarbons in the extracts of absorber-01 and absorber-02 were 96.95 and 92.78% (wt.) on a solvent-free basis, while the bottom stream of absorber-03 was enriched in oxygenated compounds with concentrations of up to 32.66% (wt.) on a solvent-free basis, showing that the organic liquid products (OLP) were deacidified and SC-CO₂ was able to deacidify the OLP and obtain fractions with lower olefin contents. The best deacidifying condition was obtained at 333 K, 140 bar, and (S/F) = 17.     

Magnetic and crystallographic properties of the system Fe2P1−xAsx

The crystallographic and magnetic properties of the system Fe₂P_1?xAs_x were studied between 0 ? x ? 0.65. The end member Fe₂P was prepared by both direct combination of the elements and electrolysis of fused salts. The products obtained showed similar crystallographic properties and were found to be stoichiometric. Differences in the magnetic properties were attributed to carbide impurities present in the samples prepared by electrolysis. The substitution of arsenic takes place preferentially on the anion_I site. The cell volume was found to increase monotonically with arsenic substitution, and the observed magnetic properties were interpreted on the basis of the Stoner model for itinerant electrons.     

The electrophilic addition of thiols to olefins: A theoretical and experimental study

Density functional theory with the B3LYP hybrid functional and 6–31G* basis set was used to study the geometric and electronic structure of H₂C = CHR (R = H, CH₃, C₂H₅, C₃H₇, C₄H₉, and C₅H₁₁) olefins, their carbocations formed in the addition of the proton to the olefins, R′-S-H aliphatic thiols (R′ = H, CH₃, C₂H₅, and C₃H₇), the products of the addition of thiols to carbocations, and the final products of the addition of thiols to olefins. The proton affinity of the olefins and the products of the addition of thiols to olefins was calculated. The conclusion was drawn that the limiting stage in the nonradical addition of thiols to olefins catalyzed by acids was proton transfer from the protonated reaction product to the olefin. The theoretical results were compared with the experimental data on the electrophilic addition of polymercaptan to heptene-1.     

Thermal decomposition of barium(II) tetraphenylborate

Barium(II) tetraphenylborate, Ba(Bph₄))₂·4H₂O was prepared, and its decomposition mechanism was studied by means of TG and DTA. The products of thermal decomposition were examined by means of gas chromatography and chemical methods. A kinetic analysis of the first stage of thermal decomposition was made on the basis of TG and DTG curves and kinetic parameters were obtained from an analysis of the TG and DTG curves using integral and differential methods. The most probable kinetic function was suggested by comparison of kinetic parameters. A mathematical expression was derived for the kinetic compensation effect.     

Phenylarsenic(III) complexes of 2-(2-hydroxyphenyl)benzothiazolines

Equimolar reactions of PhAs(OMe)₂ (prepared in situ) and 2-(2-hydroxyphenyl)benzothiazolines LH₂ give the addition products PhAs(OMe)₂LH₂, while equimolar reactions of PhAsCl₂ with Na₂L yield substitution products PhAsL. All these derivatives have been characterized by elemental analyses and their plausible structures have been established on the basis of physico-chemical, IR, and NMR (¹H and ¹³C) spectral studies. © 2003 Wiley Periodicals, Inc. 15:92–96, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.10220