Study of the thermal decomposition of solids in a fluidized bed, III

The influence of the air humidity upon the thermal decomposition of diammonium hydrogen phosphate was studied in a fluidized bed, under isothermal conditions. It was found that the increase of the decomposition rate is influenced directly by the partial pressure of the water vapour in the air, and indirectly by the working temperature. The moisture effect is explained by the salt hydrolysis in the water condensed on the grain surface. The energy of activation of the thermal decomposition decreases when the air humidity increases.

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Zusammenfassung Der Einfluß der Luftfeuchtigkeit auf die thermische Zersetzung des Diammoniumhydrogenphosphats wurde in fluidisiertem Bett unter isothermen Verhältnissen studiert. Die Zunahme der Zersetzungsgeschwindigkeit war direkt proportional dem partialen Wasserdampfdruck in der Luft und indirekt proportional der Arbeitstemperatur. Diese Wirkung wird durch Salzhydrolyse in dem kondensierten Wasser an der Kernoberfläche erklärt. Die Aktivierungsenergie der thermischen Zersetzung nimmt mit zunehmendem Feuchtigkeitsgehalt ab.

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Résumé On a étudié l'influence de l'humidité atmosphérique sur la décomposition thermique de (NH₄)₂HPO₄ en lit fluidisé, en conditions isothermes. La pression partielle de la vapeur d'eau dans l'air intervient directement sur l'augmentation de la vitesse de décomposition et exerce une action indirecte sur la température de travail. On a expliqué l'effet de l'humidité par l'hydrolyse du sel dans l'eau condensée à la surface des grains. La valeur de l'énergie d'activation de la décomposition thermique diminue quand l'humidité atmosphérique augmente.

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Optimal SNR for proton electron double resonance imaging

A significant problem for whole body PEDRI is the absorbed RF power in the body. In this paper the optimal pulse and field strength are determined which maximize the signal to noise ratio for a certain RF power level. Our calculations show that the relaxation times of the free radical contrast agent are the dominating factors which determine the pulse sequence and main field strength.     

Synthesis ofO-methyloximes and nitrones of a series of substituted 4-[2-hydroxy-2-(1H-1,2,4-triazol-1-ylmethyl)cyclohexylidenemethyl]-benzaldehydes and their fungicidal activity

O-Methyloximes and nitrones of a series of substituted 4-[2-hydroxy-2-(1H-1,2,4-triazol-1-ylmethyl)cyclohexylidenemethyl]benzaldehydes have been synthesized, and their fungicidal activity has been assayed. All of them exhibit low fungicidal activity in thein vitro assays and high activity in thein vivo assays; theO-methyl oximes are more active than the corresponding nitrones.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2082–2087, December, 1993.     

Die Beziehungen zwischen Adsorptionswärmen,Oberflächen-spannungen und Reaktionswärmen bei dem ReaktionstypusA starr +B gasförmig ⇄AB starr

Zusammenfassung Wird die gesamte Energietönung eines Vorganges vom TypusA starr +B gasförmig AB starr mitE ₁ bezeichnet, die Energie der Chemoadsorption vonB anAB mitE ₂, die der Oberflächenspannung entsprechende, auf 1 Mol sich beziehende Oberflächenarbeit bei der PhaseA mitE ₃ und bei der PhaseAB mitE ₄, so besteht die BeziehungE ₁ +E ₃ –E ₂ –E ₄ =0 . Der isotherme Abbau nach derGibbsschen Funktion kann nur stattfinden, wennE ₃ vergleichsweise sehr groß (unendlich) ist, derjenige nach derLangmuirschen Funktion, wennE ₃ sehr klein (Null) ist.     

Synthesis and electrical conductivity of poly(arylene vinylene). I. Poly(2,5-dimethoxyphenylene vinylene) and poly(2,5-dimethylphenylene vinylene)

The highly conjugated aromatic polymers, poly(2,5-dimethoxyphenylene vinylene) and poly(2,5-dimethylphenylene vinylene), were obtained from their water soluble, sulfonium salt precursor polymers. Films of these polymers were reacted with either AsF₅ or I₂ vapor. Poly(2,5-dimethoxyphenylene vinylene) showed increases in electrical conductivity of up to 14 to 15 orders of magnitude for these two dopants, while an 8 to 9 order of magnitude increase was observed for poly(2,5-dimethylphenylene vinylene) with the same dopants. The synthesis of the precursor polymers, the properties and elimination reactions of films of the precursors, the doping reactions, and the conductivities of the resulting phenylene vinylene films are discussed.     

Synthesis optimization and the properties of 8-hydroxyquinoline ion-exchange resins

The preparation of oxine-containing ion-exchange resins has been treated rigorously. The reactant ratios, nature of cure, degree of cross-linking and hydrophilicity have been evaluated in terms of metal capacity and kinetics of metal uptake. The preparation of a bead polymer with good physical properties is described; stability tests show that the gel polymers must never be allowed to dry, otherwise their advantageous properties are destroyed. Stability towards acids in re-cycling procedures is excellent in terms of metal capacity, but there is some loss in water regain which equates to a slower equilibration rate with constant use.     

Approximate force constant calculations for cis-L2M(CO)4 species

A new procedure based on the criterion of maximum interaction between coupled fundamental vibrational modes has been developed to solve the energy factored force field of cis-L₂M(CO)₄ species. The results for complexes containing a wide range of metal-ligand combinations are compared with the force constants obtained by the Cotton-Kraihanzel and Jernigan methods. The CO stretching frequencies of isotopically-substituted cis-I₂Fe(CO)₄ species have been calculated as a check on the method.     

Paths for the formation of dioxin-type xenobiotics: Quantum-chemical treatment 1. Formation of polychlorobiphenylenes from polychlorobenzenes

The heats of formation of polychloroarynes (PCA's) from polychlorobenzenes (PCB's) have been calculated by the AMI method as a function of the composition and structure of the PCB's according to a two-step scheme including deprotonation with the formation of carbanions (PCCA's, H₁) and dechlorination to PCA's (H₂). The influence of the solvent on H₁ and H₂ has been evaluated in the framework of the solvaton model. It has been shown that the value of H₁ decreases as the number of C1 atoms in the PCB is increased, while H₂ increases along the same series due to the increase in the relative stability of the PCCA as the number of C1 atoms is increased. Although the dimerization of PCA's with the formation of polychlorobiphenylenes (PCBP's) is forbidden by orbital symmetry rules, calculations of fragments of the potential-energy surface have shown that this reaction takes place with an energy barrier amounting to about 1 kcal/mole.A. N. Nesmeyanov Institute of Organometallic Compounds, Russian Academy of Sciences, 117813 Moscow. Institute of Organic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 350–355, February, 1992.