Solubility in the systems Rb2SO4-H2SO4-H2O and Cs2SO4-H2SO4-H2O at 25°

Conclusions The solubility of rubidium and cesium sulfates in aqueous solutions of sulfuric acid was studied at 25°. Rubidium sulfate forms the compounds 3Rb₂SO₄· H₂SO₄, Rb₂SO₄ · H₂SO₄, Rb₂SO₄·3H₂SO₄ and Rb₂SO₄·7H₂SO₄ with sulfuric acid, while cesium sulfate forms the compounds Cs₂SO₄·H₂SO₄; Cs₂SO₄·3H₂SO₄ and Cs₂SO₄ · 7H₂SO₄.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1166–1170, June, 1968.     

Redox Equilibria in the System Fe(OH)3(H2SO4)-Na2SO3-H2O Involving Precipitation of Iron(II) Sulfite as a Fe2O3 Precursor

Experimental data on the equilibria Fe²⁺/Fe³⁺ and SO₃ ²⁻/SO₄ ²⁻ in the system Fe(OH)₃(H₂SO₄)-Na₂SO₃-H₂O are presented. The quantitative relations between the reduction of Fe(III) and the precipitation of FeSO₃·2.5H₂O as a Fe₂O₃ precursor have considered graphically.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 1, 2005, pp. 41–44.Original Russian Text Copyright © 2005 by Vasekha, Motov.     

Quasi-unary homogeneous nucleation of H2SO4-H2O

We show that the binary homogeneous nucleation (BHN) of H2SO4-H2O can be treated as quasi-unary nucleation of H2SO4 in equilibrium with H2O vapor. A scheme to calculate the evaporation coefficient of H2SO4 molecules from H2SO4-H2O clusters is presented and a kinetic model to simulate the quasi-unary nucleation of H2SO4-H2O is developed. In the kinetic model, the growth and evaporation of sulfuric acid clusters of various sizes are explicitly simulated. The kinetic quasi-unary nucleation model does not have two well-recognized problems associated with the classical BHN theory (violation of the mass action law and mismatch of the cluster distribution for monomers) and is appropriate for the situations where the assumption of equilibrium cluster distribution is invalid. The nucleation rates predicted with our quasi-unary kinetic model are consistent with recent experimental nucleation experiments in all the cases studied, while the most recent version of the classical BHN model systematically overpredicts the nucleation rates. The hydration of sulfuric acid clusters, which is not considered in the classical model but is accounted for implicitly in our kinetic quasi-unary model, is likely to be one of physical mechanisms that lead to lower nucleation rates. Further investigation is needed to understand exactly what cause the difference between the kinetic quasi-unary model and the classical BHN model.     

Nitration of pentaerythritol by HNO3-H2SO4-H2O system

Conclusions It was shown experimentally that the nitrating agent in the O-nitration of pentaerythritol by HNO₃-H₂SO₄-H₂O nitrating mixtures is not the nitronium cation but evidently the free unionized nitric acid molecule.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 134–140, January, 1970.     

273 K下Na2CO3-Na2SO4-Na2B4O7-H2O四元体系介稳相平衡的实验研究

采用等温蒸发法研究了四元体系Na2CO3-Na2SO4-Na2B4O7-H2O在273 K时的介稳相平衡及平衡液相的密度. 利用溶解度数据绘制了该四元体系273 K下的相图. 研究结果表明, 该四元体系有异成分复盐2Na2SO4·Na2CO3形成. 相图中有2个共饱点、5条单变量曲线和4个结晶相区. 4个结晶相区分别为盐Na2CO3·10H2O, Na2SO4·10H2O, Na2B4O7·10H2O和2Na2SO4·Na2CO3的结晶区. 复盐2Na2SO4·Na2CO3同时存在于包含Na2CO3-Na2SO4-H2O三元体系的其它四元体系或高元体系中. 在273 K介稳平衡相图中, 碳酸钠以Na2CO3·10H2O形式析出; 硫酸钠以Na2SO4·10H2O的形式析出; 硼酸钠的完整分子式为Na2B4O5(OH)4·8H2O. Na2CO3对Na2B4O7有盐析作用.     

Glass formation in the systems Al2(SO4)3-MSO4-H2O (M = Cd2+, Zn2+, Mg2+) and Al2(SO4)3-Fe2(SO4)3-H2O

The glass formation region boundaries were found in the systems Al₂(SO₄)₃-MSO₄-H₂O, where M = Cd²⁺, Zn²⁺, and Mg²⁺, and Al₂(SO₄)₃-Fe₂(SO₄)₃-H₂O. The causes of the differences in glass-forming ability between the studied systems were analyzed. The structures and properties of glassy Al₂(SO₄)₃ · 11H₂O and Fe₂(SO₄)₃ · 11H₂O were compared.     

A Study of Crystallization in the System TiO2(Al2O3)-H2SO4-(NH4)2SO4-H2O in Obtaining Titanium-Aluminum Tanning Agent

The conditions under which a titanium-aluminum tanning agent is obtained from sulfuric acid solutions were studied. The composition was established and the properties were studied of the forming phases.     

(H3O)Nd(SO4)2

The crystal structure of oxonium neodymium bis(sulfate), (H₃O)Nd(SO₄)₂, shows a two‐dimensional layered framework assembled from SO₄ tetrahedra and NdO₉ tricapped trigonal prisms. One independent sulfate group makes four S—O—Nd linkages, while the other makes five such connections to generate an unprecedented anhydrous anionic [Nd(SO₄)₂]⁻ layer. To achieve charge balance, H₃O⁺ cations are inserted between adjacent layers where they participate in hydrogen‐bonding interactions with the sulfate O atoms of adjacent layers.     

Dynamics of vibrational overtone excitations of H2SO4, H2SO4-H2O: hydrogen-hopping and photodissociation processes

Photochemical processes of sulfuric acid (H2SO4) and sulfuric acid monohydrate (H2SO4-H2O) following overtone excitation of the OH stretching mode are studied by classical trajectory simulations using the semiempirical PM3 potential suface in "on the fly" calculations. The main results are the following: (1) In the excitation of H2SO4 to the fifth OH-stretch overtone, hopping of the H atom between oxygen atoms is found to take place in 22% of the trajectories, only once during simulations of 400 ps. (2) All the trajectories for H2SO4 show a rapid cis-trans isomerization. (3) The photolysis of H2SO4 into SO3 + H2O takes place in 5% of the trajectories on a time scale of approximately 9 ps. (4) Only low overtone levels of H2SO4-H2O have sufficiently long lifetimes to be spectroscopically relevant. Excitation to these OH stretching overtones is found to result in the dissociation of the cluster. H hopping or dissociation of H2SO4 does not take place.     

Glass formation in the Al(IO3)3-Al2(SO4)3-H2O system

Glass-formation boundaries in the Al(IO₃)₃-Al₂(SO₄)₃-H₂O system are determined. The IR spectra of glassy and crystalline Al(IO₃)₃ · 8H₂O samples are measured. The structure and properties of glassy Al(IO₃)₃ · 10H₂O are compared to those of glassy Al₂(SO₄)₃ · 10H₂O.     

Li2SO4-K2SO4-MgSO4-H2O体系及次级体系298.15K时的热化学研究

用连续滴定量热法研究Li2SO4-K2SO4-MgSO4-H2O体系及次级体系Li2SO4-K2SO40H2O、Li2SO4-MgSO4-H2O和K2SO4-MgSO4-H2O 298.15K时在离子强度为15-0.1范围内的比热容和稀释热, 并结合Debye-Huckel焓极限公式研究离子强度在15-0.0001范围内的表观摩尔焓。     

The effect of coordinated water on the connectivity of uranium(IV) sulfate x‐hydrate: [U(SO4)2(H2O)5]·H2O and [U(SO4)2(H2O)6]·2H2O,and a comparison with other known structures

Two new solid‐state uranium(IV) sulfate x‐hydrate complexes (where x is the total number of coordinated plus solvent waters), namely catena‐poly[[pentaaquauranium(IV)]‐di‐μ‐sulfato‐κ⁴O:O′] monohydrate], {[U(SO₄)₂(H₂O)₅]·H₂O}_n, and hexaaquabis(sulfato‐κ²O,O′)uranium(IV) dihydrate, [U(SO₄)₂(H₂O)₆]·2H₂O, have been synthesized, structurally characterized by single‐crystal X‐ray diffraction and analyzed by vibrational (IR and Raman) spectroscopy. By comparing these structures with those of four other known uranium(IV) sulfate x‐hydrates, the effect of additional coordinated water molecules on their structures has been elucidated. As the number of coordinated water molecules increases, the sulfate bonds are displaced, thus changing the binding mode of the sulfate ligands to the uranium centre. As a result, uranium(IV) sulfate x‐hydrate changes from being fully crosslinked in three dimensions in the anhydrous compound, through sheet and chain linking in the tetra‐ and hexahydrates, to fully unlinked molecules in the octa‐ and nonahydrates. It can be concluded that coordinated waters play an important role in determining the structure and connectivity of U^IV sulfate complexes.     

Enthalpies of crystallization of equilibrium solid phases occurring in the system K2SO4-(NH4)2SO4-H2O at 298.15 K

The concentration dependences of the differential enthalpies of solution were measured along several crystallization paths in the above-mentioned system, and the enthalpies of crystallization of mixed crystals occurring as a stable solid phase in the system were calculated on this basis. The obtained results confirmed the existence of a region of breaking continuity in the equilibrium solid phases.

---

Zusammenfassung Für die obengennanten Systeme wurden, mehrere Kristallisationsradien entlang, die Messungen der Konzentrationsabhängigkeiten durchgeführt, die es unter differentiellen Lösungsenthalpien gibt. Auf dieses Grundlage wurden die Kristallisationenthalpien von Mischkristallen, die als stabile feste Phase vorkommen, bestimmt.Die erreichten Ergebnisse bestätigen die Tatsache, daß ein unterbrochenes Gebiet in den gleichgewichten festen Phasen vorkommt.

     

The thermodynamic characteristics of hydrogen peroxide in H2SO4-H2O solutions

The paper presents experimental data and an analysis of literature data on hydrogen peroxide forms in concentrated solutions of sulfuric acid, H₂O₂(aq), H₃O ₂ ⁺ (aq), and HSO ₅ ^? (aq). The thermodynamic constants of the parallel equilibria $\begin{array}{*{20}c} {H_2 O_2 (aq) + H_3 O^ + (aq) \Leftrightarrow H_3 O_2^ + (aq) + H_2 O (K_1 (298) = 8 \times 10^{ - 4} ),} \\ {H_2 O_2 (aq) + HSO_4^ - (aq) \Leftrightarrow HSO_5^ - (aq) + H_2 O (K_2 (298) = 1.2 \times 10^{ - 2} )} \\ \end{array} $ were determined. The activity coefficients of H₂O₂ and Henry constants for solutions of H₂O₂ in sulfuric acid were calculated.     

Experimental determination of the H2SO4/(NH4)2SO4/H2O phase diagram

We have experimentally investigated the water and sulfuric acid-rich regions of the H2SO4/(NH4)2SO4/H2O ternary liquid/solid phase diagram using differential scanning calorimetry (DSC) and infrared spectroscopy of thin films. We present the liquid/solid ternary phase diagram for temperatures below 373 K and H2SO4 concentrations below 60 wt %. We have determined two ternary eutectics and two tributary reaction points for this system in the regions studied. It is also seen that sulfuric acid tetrahydrate (SAT) forms as a metastable solid over a large concentration range. Two true binary systems have been identified: ice/letovicite and SAT/ammonium bisulfate. Finally, we have compared our results to the predictions of the aerosol inorganics model and have found significant differences both in the final melting points and in the location of some of the phase boundaries including a significant discrepancy in the invariant points predicted versus those observed.     

Improved quasi-unary nucleation model for binary H2SO4-H2O homogeneous nucleation

Aerosol nucleation events have been observed at a variety of locations worldwide, and may have significant climatic and health implications. Binary homogeneous nucleation (BHN) of H2SO4 and H2O is the foundation of recently proposed nucleation mechanisms involving additional species such as ammonia, ions, and organic compounds, and it may dominate atmospheric nucleation under certain conditions. We have shown in previous work that H2SO4-H2O BHN can be treated as a quasi-unary nucleation (QUN) process involving H2SO4 in equilibrium with H2O vapor, and we have developed a self-consistent kinetic model for H2SO4-H2O nucleation. Here, the QUN approach is improved, and an analytical expression yielding H2SO4-H2O QUN rates is derived. Two independent measurements related to monomer hydration are used to constrain the equilibrium constants for this process, which reduces a major source of uncertainty. It is also shown that the capillarity approximation may lead to a large error in the calculated Gibbs free energy change for the evaporation of H2SO4 molecules from small H2SO4-H2O clusters, which affects the accuracy of predicted BHN nucleation rates. The improved QUN model-taking into account the recently measured energetics of small clusters-is thermodynamically more robust. Moreover, predicted QUN nucleation rates are in better agreement with available experimental data than rates calculated using classical H2SO4-H2O BHN theory.     

Saure Sulfate des Neodyms: Synthese und Kristallstruktur von (H5O2)(H3O)2Nd(SO4)3 und (H3O)2Nd(HSO4)3SO4

Acidic Sulfates of Neodymium: Synthesis and Crystal Structure of (H₅O₂)(H₃O)₂Nd(SO₄)₃ and (H₃O)₂Nd(HSO₄)₃SO₄ Light violett single crystals of (H₅O₂)(H₃O)₂ · Nd(SO₄)₃ are obtained by cooling of a solution prepared by dissolving neodymium oxalate in sulfuric acid (80%). According to X‐ray single crystal investigations there are H₃O⁺ ions and H₅O₂⁺ ions present in the monoclinic structure (P2₁/n, Z = 4, a = 1159.9(4), b = 710.9(3), c = 1594.7(6) pm, β = 96.75(4)°, R_all = 0.0260). Nd³⁺ is nine‐coordinate by oxygen atoms. The same coordination number is found for Nd³⁺ in the crystal structure of (H₃O)₂Nd(HSO₄)₃SO₄ (triclinic, P1, Z = 2, a = 910.0(1), b = 940.3(1), c = 952.6(1) pm, α = 100.14(1)°, β = 112.35(1)°, γ = 105.01(1)°, R_all = 0.0283). The compound has been prepared by the reaction of Nd₂O₃ with chlorosulfonic acid in the presence of air. In the crystal structure both sulfate and hydrogensulfate groups occur. In both compounds pronounced hydrogen bonding is observed.