Structure and thermodynamic properties of nitroformic acid,nitroformyl nitrate,and ammonium nitroformate

As part of a series of investigations of molecules with large numbers of nitro groups, the structures and properties of nitroformic acid, NO₂CO₂H, nitroformyl nitrate, NO₂C(O)ONO₂, and the ion pair ammonium nitroformate, NH₄NO₂CO₂, have been determined using GX theories (X = 2, 3, 4). Minimum-energy structures, vibrational frequencies, selected bond energies, and enthalpies of formation were determined. The title substances may not have much application as high energy materials like other high-nitro compounds, but they may act as good nitrating agents since certain bonds in the molecules are of low enough energy to suggest high reactivity.     

Thermal properties of ammonium nitrate

The reproducibility of the DTA curves of ammonium nitrate as functions of its grain size and the atmosphere during the measurements was studied with a derivatograph. The temperatures and the areas of the peaks assigned to the modification transitions IV → III (peak 1), III → II (peak 2) and II → I (peak 3) were evaluated. It was found that for some unground samples the area of peak 2 decreases markedly. It has been verified that in an atmosphere of moist air the temperature of peak 1 is lowered. The temperatures of lumpy and loose samples do not differ appreciably. Statistical methods evidenced the mutual dependence of the areas of peaks 1 and 2. The possible causes of this are discussed.     

The thermodynamic properties and solvation of ammonium bromide,iodide, and nitrate in methylpyrrolidone at 298.15 K

The heat capacity and density of solutions of ammonium bromide, iodide, and nitrate in methylpyrrolidone (MP) were studied calorimetrically and densimetrically at 298.15 K. The standard partial molar heat capacities and volumes (\(\overline {C_{p_2 }^O } \) and \(\overline {V_2^O } \)) of the electrolytes in MP were calculated. The standard heat capacities \(\overline {C_{p_i }^O } \) and volumes \(\overline {V_i^O } \) of the nitrate and ammonium ions in MP were determined. The mean coordination numbers of the NH ₄ ⁺ and NO ₃ ^? ions in a solution in MP at 298.15 K were calculated.     

Thermal analysis of corrosion products formed on carbon steel in ammonium chloride solution

The influence of different ions NO₃ ^? and SO₄ ^2? on the carbon steel corrosion in ammonium chloride was investigated using mass loss measurements and potentiodynamic polarization. Corrosion products were analyzed using X-ray photoelectron spectroscopy (XPS) and simultaneous thermal and differential scanning calorimetry (TG/DSC). XPS analysis shows that the main product of corrosion is a non-stoichiometric Fe³⁺ oxyhydroxide, consisting of a mixture of FeO(OH) and FeO(OH) containing inclusions of these anions, species such as Fe³⁺O(OH,Cl^?); Fe³⁺O(OH,SO₄ ^2?); and Fe³⁺O(OH,NO₃ ^?). TG/DSC confirms the decomposition of the rusty products formed by chemical corrosion, compounds like Fe³⁺ oxyhydroxides, with β-FeOOH as the major phase, crystal structure of which may contain Cl^?, NO₃ ^?, and SO₄ ^2?—e.g., akaganeite [Fe³⁺O(OH,A)].     

A reinterpretation of the hydration of micelles of dodecyltrimethylammonium bromide and chloride in aqueous solution

The hydration of dodecyltrimethylammonium (DTAB) micelles is reinterpreted in light of the results of the companion paper (immediately preceding this paper) that showed that the location of the spin probe 16-doxylstearic acid methyl ester (16DSE) changes as a function of the aggregation number, N, of anionic micelles, i.e, that it does not conform to the zero-order model (ZOM). The ZOM requires that the NO(*) moiety diffuse throughout the Stern layer of the micelle and nowhere else. By using the ZOM as a working hypothesis, the previous interpretation (J. Phys. Chem. B 2002, 106, 1926) of 16DSE data proposed that an increasing number of alkyl chain methyl groups occupied the Stern layer as N increased. In this work, the spin probe 5-doxylstearic acid methyl ester that was found to fulfill the ZOM in anionic micelles was measured as a function of N in DTAB and was found to obey the ZOM in this cationic micelle as well. Thus, a simple model of the hydration of micelles that is successful in anionic micelles is also successful in DTAB. The previous results for 16DSE are reinterpreted here as being due to small displacements of the NO(*) moiety as a function of N.     

Thermodynamic behavior and structural properties of an aqueous sodium chloride solution upon supercooling

We present the results of a molecular dynamics simulation study of thermodynamic and structural properties upon supercooling of a low concentration sodium chloride solution in TIP4P water and the comparison with the corresponding bulk quantities. We study the isotherms and the isochores for both the aqueous solution and bulk water. The comparison of the phase diagrams shows that thermodynamic properties of the solution are not merely shifted with respect to the bulk. Moreover, from the analysis of the thermodynamic curves, both the spinodal line and the temperatures of maximum density curve can be calculated. The spinodal line appears not to be influenced by the presence of ions at the chosen concentration, while the temperatures of maximum density curve displays both a mild shift in temperature and a shape modification with respect to bulk. Signatures of the presence of a liquid-liquid critical point are found in the aqueous solution. By analyzing the water-ion radial distribution functions of the aqueous solution, we observe that upon changing density, structural modifications appear close to the spinodal. For low temperatures, additional modifications appear also for densities close to that corresponding to a low density configurational energy minimum.     

Thermal decomposition of ammonium uranates precipitated from uranyl nitrate solution with ammonium hydroxide

Thermal decomposition of ammonium uranates precipitated from uranyl nitrate solutions on addition of aqueous ammonium hydroxide under various conditions has been examined by thermogravimetry (TG), differential thermal analysis (DTA), infrared spectroscopy and X-ray diffraction study. The TG curves of all precipitates show the weight-loss corresponding to the calculated value as UO₃·NH₃·H₂O. The DTA curves of the precipitates give the endotherms at about 130, 210 and 590 °C and the exotherms at 340–420 °C. As a result, it is found that ammonium uranates thermally decompose to amorphous UO₃ at about 400 °C, and transform to U₃O₈ via β-UO₃.     

Volumetric properties of ammonium nitrate in N,N-dimethylformamide

The densities of the ammonium nitrate in N,N-dimethylformamide (DMF) mixtures were measured at T = (308.15 to 348.15) K for different ammonium nitrate molalities in the range from (0 to 6.8404) mol·kg⁻¹. From the obtained density data, volumetric properties (apparent molar volumes and partial molar volumes) have been evaluated and discussed in the term of respective ionic and dipole interactions. From the apparent molar volume, determined at various temperatures, the apparent molar expansibility and the coefficients of thermal expansion were also calculated.     

Standard enthalpy of solution of ammonium nitrate in water at 298 K

We have made calorimetric measurements of the enthalpy of solution of NH₄NO₃(c, IV) in water at 298 K, where (c, IV) indicates the crystal form of amomonium nitrate that is stable from 256 to 305 K. Results of our measurements have been combined with enthalpy of dilution values from Parker to obtain the standard enthalpy of solution of NH₄NO₃ (c, IV) in water at 298.15 K to be ΔH^o = 25.41 kJ mol^?1.     

The effects of sodium chloride on the explosive performance of ammonium nitrate

Sodium chloride (NaCl) was added to the ammonium nitrate (AN) by different mixing methods. The heat sensitivity performance and the explosive performance of AN and ammonium nitrate fuel oil (ANFO) were studied by using differential scanning calorimeter (DSC), the UN gap test and Koenen test. The results show that: When AN contained 15 % (solution mixing) and 35 % (mechanical mixing) additive, AN maximum exothermic peak increased from 286.75 to 300.63 and 307.83 °C, respectively. For the mechanical mixing, the critical values of the UN gap test and Koenen test AN were 35 and 40 %. The ANFO both were 50 %; for the solution mixing, AN were 15 and 40 %, the critical value of the UN gap test, ANFO was 25 %. AN and ANFO contain more than the critical value of additive, the AN and ANFO would not be detonated.     

Reduction of ammonium nitrate with titanium(III) chloride in acid media

Investigation of acid ammonium nitrate solutions in the presence of titanous chloride has led to a new mechanism of nitrate reduction. It is proposed that the reduction proceeds through two electron changes and terminates as nitrous oxide in solutions whose acid content is greater than 0.1 N. The stronger reducing power of the titanous buffer method previously reported arising from a direct pH affect on the titanous -titanyl couple has been discerned rather as an effect arising from different reduction products in that media. The affects of prolonged reaction at 100° and use of osmium tetroxide catalyst were examined. A pH of 4.5 and 100% excess of titanous was insufficient to reduce nitrate to ammonia quantitatively.     

Hydration numbers and the state of water in hydration spheres of magnesium chloride and magnesium sulfate solutions

An equation for determining hydration numbers and molar adiabatic compressibilities has been derived by correct thermodynamic processing of a data set comprising ultrasound velocity, density, and isobaric heat capacity in aqueous magnesium chloride and sulfate solutions for concentrations ranging from very dilute solutions to the complete solvation boundary and temperatures of 273.15?C323.15 K. One basic innovation of the derived equation consists in that it accounts for the dependence of solvation numbers on solution concentration and in that all changes experienced by the solution are associated with the solvation of a stoichiometric mixture of electrolyte ions or nonelectrolytes molecules.     

缔合溶液热力学性质与谱学性质的关联

缔合溶液具有与理想溶液显著不同的热力学和谱学性质,对于热力学和谱学的研究,有助于我们理解缔合溶液的特殊行为.谱学技术中核磁共振(NMR)、红外(IR)和拉曼(Raman)光谱是研究分子间相互作用和溶液结构等微观性质的有效方法,谱学已成为分子热力学研究体系"四面体结构"中的第四个顶点.本文对缔合溶液中热力学(汽液平衡和焓)和谱学(NMR,IR和Raman)联系的最新研究进展进行了综述,着重介绍相关的模型,如化学缔合模型、局部组成(LC)、格子流体氢键(LFHB)理论以及统计缔合流体理论(SAFT).     

Structural characterization of zinc(II) chloride in aqueous solution and in the protic ionic liquid ethyl ammonium nitrate by x-ray absorption spectroscopy

Extended x-ray absorption fine structure (EXAFS) spectroscopy has been used to investigate the species and structures existing in a series of ZnCl(2)-H(2)O-NaCl solutions with different chloride/zinc ratios and in a solution of ZnCl(2) in the protic ionic liquid ethyl ammonium nitrate (EAN). The average coordination numbers and distances of zinc species were determined from the analysis of the EXAFS data. In aqueous solution the number of chloride ions tightly bounded to Zn(2+) is significantly related to the chloride/zinc ratio, and no inner complex formation between Zn(2+) and Cl(-) ions has been detected for low ZnCl(2) concentration (0.1 and 0.2 M). Conversely, in the same concentration range (0.13 M) the ZnCl(2) species do not dissociate in EAN and the Zn(2+) first coordination shell has two chloride ions and is completed by two oxygen atoms of the nitrate anion. The results of this investigation show that notwithstanding the existence of similar characteristics between EAN and water, the solvation properties of the two solvents are markedly different.