Stability of hypobromite solutions

The stability of hypobromite solutions is governed by such factors as the concentration of hypobromite and hydroxide, light, temperature, and the presence of foreign substances. From a review of the literature it is concluded that it is impossible to obtain perfectly stable solutions. The preparation of more or less stable hypobromite solutions is described, and the dependence of the stability on various factors is determined.     

Analysis of hypobromite solutions by indicator titrations

A rapid titrimetric method is described for the determination of the three oxidizing components in 10^-1 N hypobromite solutions with only arsenic(III) as the standard reagent. Hypobromite is determined by titration with arsenic(III) in alkaline medium, with bromothymol blue, quinoline yellow or epsilon blue as reversible indicator. Bromite is determined by reaction with an excess of iodide in weakly alkaline medium, followed by titration of the formed triiodide with arsenic(III) solution and starch as indicator. Total hypobromite, bromite and bromate is determined by titration of arsenic(III) in hydrochloric acid medium, with quinoline yellow as reversible indicator. Bromate is calculated by difference.     

Radiation-induced decomposition of cyclotrimethylenetrinitramine in aqueous solutions

Radiation-induced decomposition of cyclotrimethylenetrinitramine, a representative of heterocyclic nitramines, in dilute aqueous solutions saturated with argon, air, and N₂O has been investigated. Dose dependence curves have been obtained, and the initial yields of formation of nitrite ions and hydrogen peroxide have been measured, making up 0.122 and 0.049 in deaerated solutions, 0.050 and 0.065 in aerated solutions, and 0 and 0.074 μmol/J in N₂O-saturated solutions, respectively. The main radiolysis initial steps involve the reaction of dissociative electron capture with nitro-group elimination in the form of nitrite ion and the reaction of hydrogen atom abstraction from the methylene group by hydroxyl radicals and atomic hydrogen.     

Determination of hydrazine by direct titration with hypobromite

Summary A simple, accurate and rapid method is described for the determination of hydrazine by direct titration with hypobromite using Bordeaux B as indicator. The procedure can also be employed for the determination of hypobromite and bromate by titration with standard hydrazine.

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Zusammenfassung Zur Bestimmung von Hydrazin wird die direkte Titration mit Hypobromitlösung und Bordeaux B als Indicator empfohlen. Das Verfahren ist einfach, rasch durchführbar und liefert genaue Ergebnisse. Es kann auch zur Bestimmung von Hypobromit und Bromat durch Titration mit Hydrazinlösung verwendet werden.

     

A new method for the standardisation of hypobromite

Summary The oxidation of ferrocyanide by hypobromite and the optical density of the yellow colour of ferricyanide thus developed has been studied with the aid of a Hilger Spekker Absorptiometer Model H 760. A violet filter having maximum transmission in the range of 420–450 m was used. Series of experiments showed that quantitative oxidation of ferrocyanide occurred in the p_N range 8–8.5 (bicarbonate buffer) and the colorimetric titration may be used for the standardisation of hypobromite. The results compared favourably with those obtained by amperometric titration of hypobromite against sodium arsenite as a primary standard.Sincere thanks of the authors are due to Prof. S. S. Joshi, D. Sc. (London), F. R. I. C. (London), F. N. I., F. A. Sc. for kind interest and facilities for the work.     

The solubility and kinetics of decomposition of ozone in aqueous solutions of nitrates

The influence of the concentration of NaNO₃ on the solubility of ozone in water was studied at 20, 30, and 40°C. The solubility coefficients of ozone were calculated, and the Henry constants and Sechenov coefficients determined. The Sechenov coefficients (K _c ) were found to decrease insignificantly as the temperature increased. The kinetics of dissolved O₃ transformations was analyzed. The decomposition of ozone was described by a pseudofirst-order equation with respect to salt concentration. The rate constant (k _c ) for the decomposition of ozone in the presence of NaNO₃ was found to be 3.5 × 10^?4 l mol^?1 s^?1.     

Ozone decomposition in concentrated aqueous solutions of salts

Effect of high concentrations of electrolytes (Na₂SO₄, NaCl, and NaNO₃) on the rate of ozone decomposition in water was studied. The conversion kinetics of O₃ dissolved in these solutions was analyzed. The rate constants of ozone decomposition were determined.     

Catalytic decomposition of hydrogen peroxide in alkaline solutions

Catalytic activity of carbon, platinum-supported on high-area carbon, platinum, lead ruthenate, and ruthenium oxide towards hydrogen peroxide decomposition in alkaline solution is investigated using the rotating disk electrode technique. The heterogeneous rate constant for peroxide decomposition on these catalysts is determined from the slope of log(i_L) versus time, where i_L is the diffusion-limiting current corresponding to the concentration of peroxide at a given time. The order of catalytic activity is found to be platinum>lead ruthenate>ruthenium oxide>carbon. A general reaction mechanism for the peroxide decomposition on these catalysts is also proposed.     

Chain and monomolecular decomposition of hexogen in solutions

The decomposition of hexogen dissolved in alkylaromatic hydrocarbons, alcohols, ketones, ethers, chloroform, and some other solvents occurs via the chain mechanism. This mechanism is supported by slowing down of the reaction when inhibitors are added, the solvent deuterium kinetic isotope effect, and the dependence of the rate on the reactivity of the C—H bond in solvents. The chain reaction propagates through the transfer of a free valence from the primary N-radicals formed by N—NO₂ bond dissociation to the C-centered radicals of the solvent. The solvents are inert when the N—H bond dissociation energy is >380 or <200 kJ mol^–1, and hexogen decomposition in such solvents is monomolecular.     

Nucleation versus spinodal decomposition in confined binary solutions

Basic features of spinodal decomposition, on one side, and nucleation, on the other side, and the transition between both mechanisms are analyzed within the framework of a generalized thermodynamic cluster model based on the generalized Gibbs approach. Hereby the clusters, representing the density or composition variations in the system, may change with time both in size and in their intensive state parameters (density and composition, for example). In the first part of the analysis, we consider phase separation processes in dependence on the initial state of the system for the case when changes of the state parameters of the ambient system due to the evolution of the clusters can be neglected as this is the case for cluster formation in an infinite system. As a next step, the effect of changes of the state parameters on cluster evolution is analyzed. Such depletion effects are of importance both for the analysis of phase formation in confined systems and for the understanding of the evolution of ensembles of clusters in large (in the limit infinite) systems. The results of the thermodynamic analysis are employed in both cases to exhibit the effect of thermodynamic constraints on the dynamics of phase separation processes.     

Photooxidative decomposition of sodium dodecyl sulfate in aqueous solutions

Kinetic features and the mechanism of photooxidative decomposition of sodium dodecyl sulfate in an aqueous solution under the action of pulsed short-wavelength UV light with a continuous spectrum upon introduction of hydrogen peroxide was studied.     

Computational analysis of spinodal decomposition dynamics in polymer solutions

In this work a model, composed of the nonlinear Cahn-Hilliard and Flory-Huggins theories, is used to numerically simulate the phase separation and pattern formation phenomena of oligomer and polymer solutions when quenched into the unstable region of their binary phase diagrams. This model takes into account the initial thermal concentration fluctuations. In addition, zero mass flux and natural nonperiodic boundary conditions are enforced to better reflect experimental conditions. The model output is used to characterize the evolution and morphology of the phase separation process. The sensitivity of the time and length scales to processing conditions (initial condition c) and properties (dimensionless diffusion coefficient D) is elucidated. The results replicate frequently reported experimental observations on the morphology of spinodal decomposition (SD) in binary solutions: (1) critical quenches yield interconnected structures, and (2) off-critical quenches yield a droplet-type morphology. As D increases, the dominant dimensionless wave number k increases as well, but the dimensionless transition time t from the early stage to the intermediate stage decreases. In addition, t is shortest when c is at the critical concentration, but increases to infinity when c is at one of the two spinodal concentrations. These results are found when the solute degree of polymerization N₂ is in the range 1 ≤ N₂ ≤ 100. When N₂ > 100, however, a problem of numerical nonconvergence due to diverging relaxation rates occurs because of the very unsymmetric nature of the phase diagram. A novel scaling procedure is introduced to explain the phase separation phenomena due to SD for any value of N₂ during the time range explored in this study.     

Thermal decomposition of 2,4,6-trinitrotoluene in melt and solutions

Thermal decomposition of 2,4,6-trinitrotoluene in the temperature range from 200 to 340 °C in melt and in solutions was studied. The main features of the process (high initial rates, activation energies lower than those in the gaseous phase, a higher acceleration at the catalytic stage, and the effect of nonpolar solvents on initial rates) are explained in terms of a kinetic scheme corresponding to a degenerate branched chain reaction.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 266–271, February, 1995.     

Coulometric titration of iodide and iodine with electrolytically generated hypobromite

Conditions for the quantitative coulometric titration of iodide and iodine with electrolytically generated hypobromite in the presence of borax buffer have been established. Iodide and iodine are oxidized to iodate. The method, with biamperometric indication of the equivalence point, was successfully applied for a wide range of iodide concentrations (6.21–2115μg with reliability intervals of ±0.21–±11μg) and iodine concentrations (24.26–3311μg with reliability intervals of ±0.36–±11.7μg). The determinations are accurate and sensitive even in the presence of large amounts of bromides and chlorides ($\text{Br}{}^{\mathrm{?}}\text{I}{}^{\mathrm{?}}$= 1.2·10⁶ and $\text{C}\text{l}$^?I^?=4.0·10^{3), as well as in the presence of oxidizing agents such as IO₃?, BrO₃? and CrO₄2? ($\text{I}\text{O}$₃?/I₂)=3.2·105, $\text{I}\text{O}$₃?/I₂=3.1·103, $\text{Br}\text{O}$-₃/I₂}=1.1·10⁴ and $\text{Cr}\text{O}$^2-₄/I₂=1.0·10⁴, as was confirmed by statistical tests. The oxidation mechanism under the conditions of coulometric titrations is discussed.     

Thermal decomposition studies of aqueous and nitric solutions of hydroxyurea

Hydroxyurea and its derivatives are important nonsalt forming reductants in partitioning of uranium and plutonium in the nuclear fuel reprocessing operations. There is no experimental data available in open literature describing pressurization due to the thermal decomposition of aqueous and nitric solutions of hydroxyurea at elevated temperatures. Authors studied thermal decomposition of hydroxyurea-nitric acid system and resultant pressurization at various concentrations of nitric acid in an adiabatic calorimeter in closed-vent conditions. During these experiments, pressurization was observed. In this paper, results of these experiments have been discussed.     

New data on decomposition of nitric solutions of acetohydroxamic acid

Acetohydroxamic acid (AHA) is an important complexant/reductant for Pu(IV) in the UREX process. It decomposes in the presence of nitric acid. In literature, its decomposition kinetics in nitric acid is traditionally reported as pseudo-first order reaction. In this study, new experimental data were reported for kinetics experiments under wide consecration conditions. It was found that the decomposition reaction was first order with respect to both the components hence overall second order.     

Acousto-spinodal decomposition of compressible polymer solutions: early stage analysis

The structure and dynamics of early stage kinetics of pressure-induced phase separation of compressible polymer solutions via spinodal decomposition is analyzed using a linear Euler-Cahn-Hilliard model and the modified Sanchez Lacombe equation of state. The integrated density wave and Cahn-Hilliard equations combine the kinetic and structural characteristics of spinodal decomposition with density waves arising from pressure-induced couplings. When mass transfer rate is slower that acoustic waves, concentration gradients generate density waves that cycle back into the spinodal decomposition dynamics, resulting in oscillatory demixing. The wave attenuation increases with increasing mass transfer rates eventually leading to nonoscillatory spinodal demixing. The novel aspects of acousto-spinodal decomposition arise from the coexistence of stable oscillatory density dynamics and the unstable monotonic concentration dynamics. Scaling laws for structure and dynamics indicate deviations from incompressible behavior, with a significant slowing down of demixing due to couplings with density waves. Partial structure factors for density and density-concentration reflect the oscillatory nature of acousto-spinodal modes at lower wave vectors, while the single maximum at a constant wave vector reflects the presence of a dominant mode in the linear regime. The computed total structure factor is in qualitative agreement with experimental data for a similar polymer solution.