Integral heats of solution and enthalpies of ionization of 100% nitric acid at 298 K 3. Aqueous solutions of sulfuric acid containing 70–90% H2SO4 and ionization of HNO3 as a base

The integral heats of solution of 100% HNO₃ at =0.1mole/liter in aqueous solutions of H₂SO₄ of <90% by wt. were measured. A scheme was proposed and proved for ionization of HNO₃ as a base in 82–90% aqueous solutions of H₂SO₄, according to which un-ionized HNO₃ exists in the form of an aqueous solvate H₂O-HNO₃ and the ionized form as the ion pair NO₂ ⁺·HSO₄ ^–. The value of the enthalpy of ionization of nitric acid H(NO₂ ⁺ HSO₄ ^–)=H(NO₂ ⁺·HSO₄ ^–) drops from 2.05 at 89.99% H₂SO₄ to 0.18 kcal/mole in 84.07% H₂SO₄.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 306–310, February, 1990.     

Rearrangement energies for radicals of azido nitroaromatic compounds

Dissociation energies of C–N₃ bonds have been determined on the basis of data on the enthalpies of formation for a series of azido nitroaromatic compounds and the enthalpies of formation of radicals. Using fundamental relationships of chemical physics, a procedure has been suggested to calculate the energy of rearrangement of molecule fragments into radicals on the basis of special properties of rearrangement energy and the sums of average thermochemical energies for bonds comprising radical fragment in molecule. This calculation procedure provided a possibility to determine the energy of the N₃ moiety transformation into N₃ radical and the rearrangement energies of nitroaromatic radicals.     

Enthalpies of formation of nitrodiazoles

The enthalpies of combustion for 3,4,5-trinitro-1Н-pyrazole, 1-methyl-3,4,5-trinitro-1Н-pyrazole, 3,4,5-trinitro-1Н-pyrazole ammonium salt, and ammonium salts of all isomeric dinitropyrazoles and dinitroimidazoles were measured by bomb calorimetry, and the corresponding enthalpies of formation were calculated. The partial contributions to the enthalpies of formation of structurally related compounds were calculated for trinitropyrazole, trinitropyrazolate anion, and anions of isomeric dinitropyrazole and dinitroimidazoles.     

Evolution of the diffusion-induced flow over a sphere submerged in a continuously stratified fluid

The problem of the stabilization of the diffusion-induced flow over a sphere submerged in a continuously stratified fluid is solved using both asymptotic and numerical methods. The analytical solution describes the structure of the main convective cells, including thin meridional jets flowing along the surface and plumes spreading from the flow convergence regions above the upper and lower poles of the sphere which gradually return the fluid particles to the neutral buoyancy horizon. The total width of the flows adjacent to the surface exceeds the thickness of the salinity deficit layer or the density boundary layer. The numerical solution of the complete problem in the nonlinear formulation describes the main convective cells and two systems of unsteady integral waves formed in the vicinity of the sphere poles. At large times, out of the entire system of internal waves only those nearest to the neighborhood of their horizon of formation remain clearly defined. The calculated flow patterns are in agreement with each other and the data of shadow visualization of the stratified fluid structure near a submerged obstacle at rest.     

Fabrication and study of properties of magnetite nanoparticles in hybrid micelles of polystyrene-<Emphasis Type="Italic">block</Emphasis>-polyethylene oxide and sodium dodecyl sulfate

Magnetite nanoparticles have been formed for the first time in hybrid micelles of polystyrene-block-polyethylene oxide and sodium dodecyl sulfate in water by ultrasonic treatment at room temperature. An analysis by small-angle X-ray scattering and transmission electron microscopy (TEM) showed that magnetite nanoparticles in hybrid micelles of block copolymer and sodium dodecyl sulfate are polydesperse (have sizes from 0.5 to 20 nm). The specific magnetization of solid samples has been measured.     

Modification of the Quantitative Method of Flavonoid Determination in the Goldenrod Canadensis (Solidago Canadensis) Herb

Moscow University Chemistry Bulletin - The technique of the quantitative determination of the sum of flavonoids based on rutin in the Canadian Goldenrod herb is modified by the method of...     

Thermochemical properties of the salts of picric and dinitrobenzoic acids

The enthalpies of formation and dissolution of the ammonium and guanidinium picrates and dinitrobenzoate were determined by precision calorimetry. On the basis of the data obtained, the enthalpies of formation of the anions of the acids in indefinitely diluted aqueous solutions were calculated and the enthalpy of formation of potassium picrate was estimated.