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.     

3-D phase diagram of HPC/H2O/H3PO4 tertiary system

A 3-D phase diagram of the HPC/H₂O/H₃PO₄ tertiary system against various temperatures was established. Four distinct phases—the completely separated phase (S), the cloudy suspension phase (CS), the liquid crystalline miscible phase (LC), and the isotropically miscible phase (I)—were identified. The S phase shrank as the temperature increased, revealing that the HPC solubility increased with temperature, regardless of the LCST (lower critical solution temperature) characteristic. The addition of H₃PO₄ suppressed the formation of LC phase. However, as the temperature was raised sharply from 50 to 70?°C, the LC phase could only be maintained at high H₃PO₄ concentration region; it was a triangular shape, and the top apex of the triangle was the temperature-invariant L* point (HPC/H₂O/H₃PO₄ 38/9/53?wt%). The CS phase expanded considerably into the H₂O-rich but H₃PO₄-poor region when the temperature continued to increase over 48?°C. The LCST points of the CS phase that contained 0 and 15?wt% of H₃PO₄ were 34 and 38?°C, respectively. These CS results demonstrate that H₃PO₄ suppresses the occurrence of LCST behavior. Additionally, the binodal curve exhibits a weak or even zero dependence of binodal temperature on the HPC concentration at HPC concentrations of less than 30?wt% in a pure water system. A hypothesis concerning the sequential desorption of water molecules was proposed to explain such behavior.     

Mössbauer study of the thermal decomposition of co-precipitated Fe/NH4/2/SO4/2.6H2O and Ni/NH4/2/SO4/2.6H2O

Using Mössbauer spectroscopy, the thermal decomposition products of co-precipitated Fe/NH_4/2/SO_4/2.6H₂O and Ni/NH_4/2/SO_4/2.6H₂O for two hours at various temperatures in open air have been studied and identified. It has been found that NiFe₂O₄, formed at 900 °C and 1100 °C, has been the final product.     

Thermal behaviour of [CoCO3(NH3)4]2SO4 · 3H2O

The thermal behaviour of [CoCO₃(NH₃)₄]₂SO₄ · 3H₂O was studied using X-ray diffraction diagrams, DTA, TG and heating at constant temperatures for different periods of time. The X-ray study was made in order to characterize with the powder diagrams the phases obtained and to follow the reactions of the complex when heated in air up to 800. A parallel infrared spectral study was also made. The results obtained by the various experimental methods were compared with the theoretical weight losses.

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Zusammenfassung Das thermische Verhalten von [CoCO₃(NH₃)₄]₂SO₄ · 3H₂O wurde durch Röntgendiffraktion, DTA, TG und Erhitzen auf gleiche Temperatur in verschiedenen Zeiten, untersucht. Die röntgenographische Prüfung diente zum Kennzeichnen der erhaltenen Phasen durch Pulverdiagramme und zur Verfolgung der in Luft bis 800 im Komplex verlaufenden Reaktionen. Es wurde parallel auch eine Prüfung durch infrarote Spektroskopie unternommen. Die auf verschiedene Weise erhaltenen Ergebnisse wurden miteinander in Einklang gebracht.

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Résumé On a étudié le comportement thermique de [CoCO₃(NH₃)₄]₂SO₄ · 3H₂O par diffraction de rayons X, ATD et ATG avec maintien en thermostat. L'étude par rayons X a été menée dans le but de caractériser les phases obtenues par leur diagramme de poudre et de suivre les réactions données par le complexe chauffé dans l'air jusqu'à 800. En raison de l'impossibilité de suivre l'évolution thermique par rayons X, une étude parallèle a été effectuée par spectrographie infrarouge. On a essayé de rapprocher les résultats obtenus à l'aide de ces différentes méthodes.

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[CoCo₃(NH₃)₄]₂SO₄·3H₂O , , , . 800. . , , , .

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This work has been carried out, in part, through the Ayuda para el Fomento de la Investigación en la Universidad.     

(NH4)3[VO2(SO4)2(H2O)2]·1.5H2O

The title compound, tri­ammonium cis‐di­aqua‐cis‐dioxo‐trans‐disulfatovanadate 1.5‐hydrate, was obtained by oxidizing V^IV to V^V in a 2 M sulfuric acid solution of vanadyl­ sulfate and adding ammonium sulfate. Here, the V atom is sandwiched by two sulfate groups by corner‐sharing to form a discrete [VO₂(SO₄)₂(OH₂)₂]^3? anion. The water mol­ecules occupy cis positions in the equatorial plane of the vanadium octahedron.     

Single freezing and triple melting of micrometre-scaled (NH4)2SO4/H2O droplets

Atmospheric aerosol droplets containing NH(4)(+) and SO(4)(2-) ions are precursors of cirrus ice clouds. However, the low-temperature phase transformation of such droplets is not understood yet. Here we show for the first time that micrometre-scaled (NH(4))(2)SO(4)/H(2)O droplets produce one freezing event but three melting events which are the melting of (i) pure ice, (ii) eutectic ice/(NH(4))(2)SO(4), and (iii) eutectic ice/(NH(4))(3)H(SO(4))(2). We also find that the melting of ice/(NH(4))(3)H(SO(4))(2) consists of two eutectic melting events, presumably ice/letovicite-II and ice/letovicite-III.     

Raman observation of the interactions between NH4+, SO4(2-), and H2O in supersaturated (NH4)2SO4 droplets

High signal-to-noise ratio (S/N) Raman spectra of (NH(4))(2)SO(4) droplets deposited on a quartz substrate were obtained from dilute to supersaturated states upon decreasing the relative humidity (RH). When the molar water-to-solute ratio (WSR) decreases from 16.8 to 3.2, the v(1)-SO(4)(2-) band changes very little, that is, showing a red-shift of only about 1 cm(-1) (from 979.9 to 978.8 cm(-1)) and an increase of its full width at half-maximum (fwhm) from 8.3 to 9.8 cm(-1). Other vibration modes such as v(2)- and v(4)-SO(4)(2-) bands appear almost constantly at 452 and 615 cm(-1). Such kind of a spectroscopic characteristic is different from previous observation on other cations, indicating that the interactions between SO(4)(2-) and NH(4)+ in supersaturated states are similar to those between SO(4)(2-) and H(2)O in dilute states. After fitting the Raman spectra with Gaussian functions in the spectral range of 2400-4000 cm(-1), we successfully extracted six components at positions of 2878.7, 3032.1, 3115.0, 3248.9, 3468.4, and 3628.8 cm(-1), respectively. The first three components are assigned to the second overtone of NH(4)+ umbrella bending, the combination band of NH(4)+ umbrella bending and rocking vibrations, and the NH(4)+ symmetric stretching vibration, while the latter three components are from the strongly, weakly, and slightly hydrogen-bonded components of water molecules, respectively. With a decrease of the RH, the proportion of the strongly hydrogen-bonded components increases, while that of the weakly hydrogen-bonded components decreases in the droplets. The coexistence of strongly, weakly, and slightly hydrogen-bonded water molecules must hint at a similar hydrogen-bonding network of NH(4)+, SO(4)(2-), and H(2)O to that of pure liquid water in supersaturated (NH(4))(2)SO(4) droplets.     

氨再生条件对V2O5/AC同时脱硫脱硝活性的影响

对烟气同时脱硫脱硝过程中吸附SO2后的活性炭载V2O5（V2O5/AC）催化 吸附剂在含NH3气氛下的再生条件进行了考察,发现3%～5%NH3/Ar气氛、300℃、60min再生可有效恢复V2O5/AC的脱硫活性,并明显提高其脱硝活性。基于对SO2和NO的脱除率、再生后V2O5/AC的硫质量分数以及FT IR谱图分析发现,NH3的存在对V2O5/AC所吸附硫的脱附行为没有明显影响,但可显著改变V2O5/AC的表面化学性质,有利于烟气脱硫;NH3还可在V2O5/AC表面储存,显著促进脱硝。     

共聚焦拉曼光谱研究过饱和硝酸铵液滴中NH4+, NO3- 和H2O之间的相互作用

将硝酸铵液滴沉积在石英基底上,通过降低该液滴周围环境的相对湿度,测定了该液滴由低浓度直至过饱和状态下高信噪比的拉曼光谱.其中,相对湿度的变化可以精确控制液滴浓度的改变.在相对湿度(RH)由72.1%降低至37.9%的过程中,硝酸铵液滴v1-NO-3峰位保持在1048cm-1,半峰宽为10cm-1.该现象表明NO-3周围的水分子被NH4+取代后不会对v1-NO-3造成影响,说明水分子和NH4+所形成的氢键具有相同的强度.对2500-4000cm-1范围内的拉曼光谱进行成分分析,2890、3090、3140、3220、3402及3507cm-1分别被指认为NH+4伞状弯曲振动的泛频、NH+4伞状弯曲振动与摇摆振动的组合谱带、NH+4的对称伸缩振动、NH+4的反对称伸缩振动、水峰中强氢键成分和弱氢键成分.从拟合结果得出:强氢键在氢键结构中所占百分含量随液滴相对湿度的降低而减少,弱氢键所占百分含量随液滴相对湿度的降低而增加.该变化趋势是NO-3和NH+4之间复杂相互作用的结果.     

Thermal behaviour and vibrational spectra of (NH4)3Ga(C2O4)3 · 3H2O and (NH4)3Al(C2O4)3 · 3H2O

The IR and Raman spectra and the thermal behaviour of the isomorphous compounds (NH₄)₃Ga(C₂O₄)₃·3H₂O and (NH₄)₃Al(C₂O₄)₃·3H₂O were investigated. Detailed stoichiometries, sustained by TG, DTA and IR spectroscopic analyses, were found in both cases. Different results, associated with the different polarizing powers of the metal cations, were obtained. The first evidence was found of the formation of basic gallium carbonates.     

A hydrothermal investigation of the 1/2V2O5-H2C2O4/H3PO4/NH4OH system: synthesis and structures of (NH4)VOPO(4).1.5H2O, (NH4)0.5VOPO(4).1.5H2O, (NH4)2[VO(H2O)3]2[VO(H2O)][VO(PO4)2](2).3H2O, and (NH4)2[VO(HPO4)]2(C2O4).5H2O

The 1/2V2O5-H2C2O4/H3PO4/NH4OH system was investigated using hydrothermal techniques. Four new phases, (NH4)VOPO(4).1.5H2O (1), (NH4)0.5VOPO(4).1.5H2O (2), (NH4)2[VO(H2O)3]2[VO(H2O)][VO(PO4)2]2.3H2O (3), and (NH4)2[VO(HPO4)]2(C2O4).H2O (4), have been prepared and structurally characterized. Compounds 1 and 2 have layered structures closely related to VOPO(4).2H2O and A0.5VOPO4.yH2O (A = mono- or divalent metals), whereas 3 has a 3D open-framework structure. Compound 4 has a layered structure and contains both oxalate and phosphate anions coordinated to vanadium cations. Crystal data: (NH4)VOPO(4).1.5H2O, tetragonal (I), space group I4/mmm (No. 139), a = 6.3160(5) A, c = 13.540(2) A, Z = 4; (NH4)0.5VOPO(4).1.5H2O, monoclinic, space group P2(1)/m (No. 11), a = 6.9669(6) A, b = 17.663(2) A, c = 8.9304(8) A, beta = 105.347(1) degrees, Z = 8; (NH4)2[VO(H2O)3]2[VO(H2O)][VO(PO4)2]2.3H2O, triclinic, space group P1 (No. 2), a = 10.2523(9) A, b = 12.263(1) A, c = 12.362(1) A, alpha = 69.041(2) degrees, beta = 65.653(2) degrees, gamma = 87.789(2) degrees, Z = 2; (NH4)2[VO(HPO4)]2(C2O4).5H2O, monoclinic (C), space group C2/m (No. 12), a = 17.735(2) A, b = 6.4180(6) A, c = 22.839(2) A, beta = 102.017(2) degrees, Z = 6.     

NH4VO3在NH4H2PO4-H2O和(NH4)3PO4-H2O体系中的溶解度

采用等温溶解法测定了偏钒酸铵(NH₄VO₃)在NH₄H₂PO₄-H₂O和(NH₄)₃PO₄-H₂O体系中T = 298.15-328.15 K时的溶解度以及溶液的密度和pH值。结果表明, NH₄VO₃的溶解度随着(NH₄)₃PO₄或NH₄H₂PO₄溶液浓度的增大,先降低后升高,这是由于同离子效应、化学反应平衡及离子活度的共同作用。比较T = 298.15K时, NH₄VO₃分别在NH₄H₂PO₄-H₂O、(NH₄)₂HPO₄-H₂O和(NH₄)₃PO₄-H₂O体系中溶解度,发现在相同的磷酸盐浓度下, NH₄VO₃的溶解度在NH₄H₂PO₄-H₂O体系中最大,在(NH₄)₃PO₄-H₂O体系中居中,在(NH₄)₂HPO₄-H₂O体系中最小。进一步地,在T = 298.15 K和磷酸盐浓度C = 0.5 mol·kg^-1时,结合pH值和反应溶度积常数K_SP等计算三个体系中的平均离子活度系数(γ_±),发现γ_±值在(NH₄)₂HPO₄-H₂O体系中最大,在(NH₄)₃PO₄-H₂O体系中居中,在NH₄H₂PO₄-H₂O体系中最小,与溶解度规律一致。     

(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.     

Subsolidus phase diagram of the binary system (n-C n H2n+1NH3)2CoCl4

The perovskite-type layered compounds decylammonium tetrachlorocobaltate (n-C₁₀H₂₁NH₃)₂CoCl₄ and dodecylammonium tetrachlorocobaltate (n-C₁₂H₂₅NH₃)₂CoCl₄ exist the solid–solid phase transition in the temperatures range 330–380 K. These laminar materials contain bilayers sandwiched between metal halide layers. The experimental subsolidus binary phase diagram of (n-C₁₀H₂₁NH₃)₂CoCl₄–(n-C₁₂H₂₅NH₃)₂CoCl₄ has been established over the whole composition range by differential thermal analysis and X-ray diffraction. In the phase diagram, one intermediate compound (n-C₁₀H₂₁NH₃) (n-C₁₂H₂₅NH₃)CoCl₄ at $ W_{{{\text{C}}_{ 1 0} {\text{Co}}}} \% = 50. 9 2 $ and two eutectoid invariants points at $ W_{{{\text{C}}_{ 10} {\text{Co}}}} \% = 2 9. 8 3 $ and $ W_{{{\text{C}}_{ 10} {\text{Co}}}} \% = 7 7. 9 8 $ were observed, two eutectoids temperatures are about 343 ± 1 and 340 ± 1 K. There are three noticeable solid solution ranges (α, β, γ) at the left and right boundary and middle of the phase diagram.     

The phase diagram and supercooling conditions for the Ca(NO3)2−CaCl2−H2O system

The liquidus temperature and induction periods were measured for crystallization in a system of calcium nitrate, calcium chloride, and water over a concentration range of 5–20 mole% Ca(II), i.e., R=4–18 [R=moles H₂O/moles Ca(II)] and y_cl=0–1 [y_cl=moles Cl^–/moles (NO ₃ ^– +Cl^–)]. A ternary phase diagram was constructed, and qualitative dependences of the supercooling at which the solution began to crystallize on the system composition were found. A wide range of stability toward crystallization was found for solutions withR=4–10 and y_cl=0–0.7 The relationships between the system stability toward crystallization and the viscosity, glass-transition temperature, and the liquidus temperature are discussed.     

Simultaneous solubility of SO2 and NH3 in (salt + H2O) and enthalpy change upon dilution of (SO2 + NH3 + salt + H2O) in (salt + H2O) {salt = (NH4)2SO4 or Na2SO4}: Experimental results and model predictions

The simultaneous solubility of sulfur dioxide and ammonia in aqueous solutions of (ammonium sulfate or sodium sulfate) was measured by a synthetic method in the temperature range from 313.6 to 373.2 K and at pressures up to 2.5 MPa. Furthermore, the enthalpy change upon diluting aqueous solutions of sulfur dioxide, ammonia and (ammonium sulfate or sodium sulfate) in aqueous solutions of the same salt was measured in a batch calorimeter at about 313 and 352 K. The experimental results are used for comparison with predictions from a thermodynamic model for the vapor–liquid equilibrium and the enthalpy of dilution of those chemical reacting systems. In that model, activity coefficients are calculated from Pitzer's molality-scale-based Gibbs excess energy model, where all interaction parameters are either adopted from previous investigations on the properties of the binary and ternary sub-systems (if available) or they are neglected (if they are not available).     

吡嗪桥连异三核配合物的合成及晶体结构

Ag(Ⅰ)配合物的几何构型多变,最常见的是配位数为2的线性构型和配位数为4的四面体构型。前者如Ag(NH_3)_2~+及Ag(CN)_2,后者如[Ag(SC(CH_3)NH_2)_4]Cl、[(Ph_3)Ag(Cl)]和[(Ph_3MeP)_3Ag(BH_4]等。配位数为4的平面四方构型却罕见,只在当有一定刚性的四氮杂环十四烷和Ag(Ⅰ)生成配合物时才是平面四方构型。 本文报道一种新型异三核含银配合物的合成及其晶体结构,其中Ag是平面四方构型。     

On the preparation and thermal stability of (NH4)3 VOF6.1.5H2O and (NH4)3NbOF6.1.5H2O

(NH₄)₃VOF₆ and (NH₄)₃NbOF₆ were prepared by a simple solid state route and their thermolysis studied. It is concluded that both these compounds have water of hydration, their structures are different and they show first order phase transitions.