共查询到20条相似文献,搜索用时 15 毫秒
1.
The results of a differential scanning calorimetric study of the transitions involving the various polymorphs of Na2SO4 are described. They are discussed in the light of their crystal structures and also in conjunction with more recently published data regarding these transitions.
Zusammenfassung Die Ergebnisse einer mit Differentialabtastkalorimetrie durchgeführten Untersuchung der Übergänge verschiedener Polymorphe von Na2SO4 werden beschrieben. Sie werden im Hinblick ihrer Kristallstrukturen und im Zusammenhang mit verschiedenen unlängst veröffentlichten Daten bezüglich dieser Übergänge diskutiert.
Résumé On décrit les résultats de l'étude, effectuée par analyse calorimétrique différentielle, des transitions mettant en jeu les diverses formes polymorphes de Na2SO4. Les résultats sont discutés en tenant compte des données récemment publiées sur ces transitions.
. , .相似文献
2.
《European Journal of Solid State and Inorganic Chemistry #》1998,35(10-11):595-606
Quenching of Na2SO4 - CaSO4 melts down to room temperature results in different forms of metastable solid solutions dependent on the CaSO4 content. The transformation of these solid solutions into stable phases were investigated after various times and temperatures by X-ray powder diffraction and thermal analyses. An equilibrium phase diagram is derived, which is in accordance with all experimental facts. 相似文献
3.
Amir A. Mehrdad Sharif Ali M. Astaraki Parviz Aberoomand Azar Saeed Abedini Khorrami Shahram Moradi 《Arabian Journal of Chemistry》2012,5(1):41-44
The effect of NaCl and Na2SO4 concentrations in aqueous phase on the phase inversion temperature (PIT) in nanoemulsions of water/Brij30/n-hexadecane system has been studied separately, and then compared. The variation of conductivity with temperature was measured by Cyber Scan PC510 conductivity meter for emulsions with 20 wt% hexadecane and 8 wt% Brij30 concentration and different concentrations of NaCl and Na2SO4 in aqueous phase. The results showed that with increasing concentrations of NaCl and Na2SO4 in aqueous phase, the PIT of nanoemulsions decreases. The effect of the elevation of concentration on the decrease of PIT was more for Na2SO4 in aqueous phase than NaCl with equal concentrations. 相似文献
4.
The polarized absorption spectrum of the chromate ion has been measured at liquid hydrogen and helium temperatures. With chromate dissolved in K2SO4 evidence is found for two orbitally allowed 1
A
11
T
2 electronic absorption bands. The first band is split into three sublevels with the 0-0 lines located at 26,316 cm–1, 26,441 cm–1 and 26,610 cm–1. Built upon the 0-0 lines is seen a simple progression in quanta of 783 cm–1. The second transition is nearly featureless, and is found at 34,000 cm–1 to 44,000 cm–1. The two bands are assigned as primarily t
12e and as 3t
22e respectively.VO
4
dissolved in Na3PO4 · 12H2O showed at liquid nitrogen temperature a broad featureless band found between 30,000 and 40,000 cm–1.
On leave of absence from Anorganisch Chemisch Laboratorium der Universiteit, Amsterdam. 相似文献
Zusammenfassung Das polarisierte Absorptionsspektrum des Chromations wurde bei den Temperaturen des flüssigen Wasserstoffs und Heliums gemessen. Für Chromat in K2SO4 werden zwei erlaubte Absorptionsbanden 1 A 11 T 2 gefunden. Die erste Bande ist dreifach aufgespalten, ihre 0-0 Linien liegen bei 26316 cm–1, 26441 cm–1 und 26610 cm–1. Von den 0-0 Linien ausgehend zeigt sich eine einfache Zunahme der Werte um 783 cm–1. Der zweite Übergang ist nahezu strukturlos, er liegt zwischen 34000 cm–1 und 44000 cm–1. Die beiden Banden werden überwiegend t 12e bzw. 3t 22e zugeordnet. VO 4 in Na3PO4 · 12H2O zeigt bei der Temperatur des flüssigen Stickstoffs eine breite strukturlose Bande zwischen 30 000 und 40 000 cm–1.
Résumé Le spectre d'absorption en lumière polarisée de l'ion chromate a été mesuré aux températures de l'hydrogène et de l'hélium liquide. Pour le chromate dissous dans K2SO4 on met en évidence deux bandes d'absorption électronique de transition orbitale permise 1 A 11 T 2. La première bande est séparée en trois sous niveaux dont les raies 0-0 se trouvent à 26,316 cm–1, 26,441 cm–1 et 26,610 cm–1. A partir des raies 0-0 on distingue une période de 783 cm–1. La seconde bande est presque non structurée et s'étend de 34,000 cm–1 à 44,000 cm–1. Les deux bandes sont décrites comme t 12e et 3t 22e respectivement.VO 4 dissous dans Na3PO4 · 12H2O révèle à la température de l'azote liquide une large bande sans structure entre 30,000 et 40,000 cm–1.
On leave of absence from Anorganisch Chemisch Laboratorium der Universiteit, Amsterdam. 相似文献
5.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1984,40(11-12):1063-1069
Raman spectra of single crystal (NH4)2ZnCl4 at 300 and 105K at different polarizations are reported and analysed in view of previously reported structural data. The experimental observations suggest that the free oriented gas model is applicable for group theoretical analysis of the vibrational modes in this system at room temperature. It is also concluded that the space group for the room temperature phase III is C2s instead of C92v. The temperature dependence of thermosensitive bands shows discontinuities at 267 and 194 K. The structure in the new phase VI below 194 K is suggested to be triclinic. 相似文献
6.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1989,45(8):795-802
The room temperature polarized Raman spectra of single crystal Na2(SeO4)0.15(SO4)0.85 are assigned, based on a factor group analysis. The internal optic modes of the oxyanions are responsible for Raman bands from 113O to 350 cm−1 and the external optic modes are found between 270 and 50cm−1. The symmetry-based and anion isotope abundance-based assignments of these bands are discussed. 相似文献
7.
Formation of Solid Solutions of Na2SO4 in the High-temperature Form of Na3PO4 The high-temperature form of Na3PO4 solves up to 70 mole-% Na2SO4 maintaining the type of crystal structure. The lattice constants increase from 742.3(1) pm (pure Na3PO4) to 749.1(2) pm for Na3?x(PO4)?x(SO4)x (x = 0.7). The high-temperature form, in the case of pure Na3PO4 stable above 325°C, is stabilized at room-temperature by doping with small amounts of Na2SO4. 相似文献
8.
《Electrochemistry communications》2008,10(10):1652-1655
The electrochemical performances of activated carbon (AC) in 0.5 mol/l Li2SO4, Na2SO4 and K2SO4 aqueous electrolytes were investigated. The cyclic voltammetric results at different scan rates show that the rate behaviors of AC in the three electrolytes improve in the order of Li2SO4 < Na2SO4 < K2SO4. This improvement can be mainly ascribed to the following two reasons: (1) the decreasing equivalent series resistance in the order of Li2SO4 > Na2SO4 > K2SO4, which is the main factor influencing the maximum output power, and (2) the increasing migration speed of hydrated ions in the bulk electrolyte and in the inner pores of AC electrode in the order of Li+ < Na+ < K+. Their cycling behaviors do not show any differences in capacitive fading. The above results provide valuable information to explore new hybrid supercapacitors. 相似文献
9.
In the present paper, the possible ion associated species in pure Na(2)SO(4) and mixed Na(2)SO(4)/MgSO(4) aqueous solutions are investigated via the ab initio method at the HF/6-31+G? level. The vibrational v(1)-SO(4)(2-) band is analyzed. For the unhydrated species, when the number of metal ions around the SO(4)(2-) ion is less than 3, the dominating effect to the v(1)-SO(4)(2-) band is the polarization of the cations, while the M-O bonding will be dominating as the number is equal to or more than 3. For the hydrated species, the coordinated structures of the Na(+) ion in all ion pairs are not stable due to the strong effect of the SO(4)(2-) ion but relatively stable in the triple ion (TI) clusters since there are fewer vacant hydration sites around the SO(4)(2-). The v(1)-SO(4)(2-) frequencies are close to that of the hydrated SO(4)(2-) ion in the ion pairs and larger in both Na(2)SO(4) and Na(2)SO(4)/MgSO(4) TI clusters. On the basis of our calculated results, the evolvement of Raman spectra in the Na(2)SO(4)/MgSO(4) droplet with the molar ratio of 1:1 is explained. 相似文献
10.
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. 相似文献
11.
The role of different H-bonds in phases II, III, IV, and V of triammonium hydrogen disulfate, (NH(4)(+))(3)H(+)(SO(4)(2)(-))(2), has been studied by X-ray diffraction and (1)H solid-state MAS NMR. The proper space group for phase II is C2/c, for phases III and IV is P2/n, and for phase V is P onemacr;. The structures of phases III and IV seem to be the same. The hydrogen atom participating in the O(-)-H(+).O(-) H-bond in phase II of (NH(4)(+))(3)H(+)(SO(4)(2)(-))(2) at room temperature is split at two positions around the center of the crucial O(-)-H(+).O(-) H-bonding, joining two SO(4)(2)(-) tetrahedra. With decreasing temperature, it becomes localized at one of the oxygen atoms. Further cooling causes additional differentiation of possibly equivalent sulfate dimers. The NH(4)(+) ions participate mainly in bifurcated H-bonds with two oxygen atoms from sulfate anions. On cooling, the major contribution of the bifurcated H-bond becomes stronger, whereas the minor one becomes weaker. This is coupled with rotation of sulfate ions. In all the phases of (NH(4)(+))(3)H(+)(SO(4)(2)(-))(2), some additional, weak but significant, reflections are observed. They are located between the layers of the reciprocal lattice, suggesting possible modulation of the host (NH(4)(+))(3)H(+)(SO(4)(2)(-))(2) structure(s). According to (1)H MAS NMR obtained for phases II and III, the nature of the acidic proton disorder is dynamic, and localization of the proton takes place in a broader range of temperatures, as can be expected from the X-ray diffraction data. 相似文献
12.
Vargas Jentzsch P Kampe B Rösch P Popp J 《The journal of physical chemistry. A》2011,115(22):5540-5546
Mg(2+), Na(+), and SO(4)(2-) are common ions in natural systems, and they are usually found in water bodies. Precipitation processes have great importance in environmental studies because they may be part of complex natural cycles; natural formation of atmospheric particulate matter is just one case. In this work, Na(2)Mg(SO(4))(2)·5H(2)O (konyaite), Na(6)Mg(SO(4))(4) (vanthoffite), and Na(12)Mg(7)(SO(4))(13)·15H(2)O (loeweite) were synthesized and their Raman spectra reported. By slow vaporization (at 20 °C and relative humidity of 60-70%), crystallization experiments were performed within small droplets (diameter ≤ 1-2 mm) of solutions containing MgSO(4) and Na(2)SO(4), and crystal formations were studied by Raman spectroscopy. Crystallization of Na(2)Mg(SO(4))(2)·4H(2)O (bloedite) was observed, and the formation of salt mixtures was confirmed by Raman spectra. Bloedite, konyaite, and loeweite, as well as Na(2)SO(4) and MgSO(4)·6H(2)O, were the components found to occur in different proportions. No crystallization of Na(6)Mg(SO(4))(4) (vanthoffite) was observed under the crystallization condition used in this study. 相似文献
13.
Synthesis and Structure of New Sodium Hydrogen Sulfates Na(H3O)(HSO4)2, Na2(HSO4)2(H2SO4), and Na(HSO4)(H2SO4)2 Three acidic sodium sulfates have been synthesized from the system sodium sulfate/sulfuric acid and have been crystallographically characterized. Na(H3O)(HSO4)2 ( A ) crystallizes in the space group P21/c with the unit cell parameters a = 6.974(2), b = 13.086(2), c = 8.080(3) Å, α = 105.90(4)°, V = 709.1 Å3, Z = 4. Na2(HSO4)2(H2SO4) ( B ) is orthorhombic (space group Pna21) with the unit cell parameters a = 9.970(2), b = 6.951(1), c = 13.949(3) Å, V = 966.7 Å3 and Z = 4. Na(HSO4)(H2SO4)2 ( C ) crystallizes in the triclinic space group P1 with the unit cell parameters a = 5.084(1), b = 8.746(1), c = 11.765(3) Å, α = 68.86(2)°, β = 88.44(2)°, γ = 88.97(2)°, V = 487.8 Å3 and Z = 2. All three compounds contain SO4 tetrahedra as HSO4? anions and additionally in B and C in form of H2SO4 molecules. The ratio H:SO4 determines the connectivity degree in the hydrogen bond system. In A , there are zigzag chains and dimers additionally connected via oxonium ions. Complex chains consisting of cyclic trimers (two HSO4? and one H2SO4) are present in B . In structure C , several parallel chains are connected to columns due to the greater content of H2SO4. Sodium cations show a distorted octahedral coordination by oxygen in all three structures, the NaO6 octahedra being “isolated” (connected via SO4 tetrahedra only) in A . Pairs of octahedra with common edge form Na2O10 dimeric units in C . Such double octahedra are connected via common corners forming zigzag chains in B . 相似文献
14.
The results of experimental study of reversible solid-state reaction Na2CO3 + BaSO4 = Na2SO4 + BaCO3 were considered. The equilibrium composition of the mixture at 550 and 600°C with 10 different initial ratios of the reactants, and the initial rate of the process were determined. The role of the Le Chatelier principle in the analysis of the thermodynamic state of the reagents was considered. The thermodynamic equilibrium constant was found from the data on the dependence of concentration equilibrium constants on the composition and the results of X-ray phase analysis using regular solution theory. 相似文献
15.
Cortez Ely V. Pessoa Adalberto Assis Adilson N. 《Applied biochemistry and biotechnology》1998,(1):661-666
Xylans are the major components of the hemicellulosic fraction of lignocellulosic biomass and their hydrolysis can be obtained
using xylanases fromPenicillium janthinellum. In this work, sugarcane bagasse hemicellulosic hydrolysate was used as the substrate for producing xylanase. The precipitation
of these enzymes was studied using ethanol and Na2SO4 as precipitating agents. Ethanol precipitation experiments were performed batchwise in concentrations ranging from 10 to
80%, pH 4.0 to 7.0, at 4áC. The concentrations used in the precipitations with Na2SO4 were from 5 to 60% at pH 5.5 and 25áC. Solubility curves as a function of xylanase activity and total protein for both precipitating
agents were made. According to the results, Na2SO4 is not appropriate for precipitating xylanases in this medium since at salt concentrations higher than 25%, the enzyme was
denaturated and at this concentration less than 80% of the enzyme and total protein were precipitated. Because of differences
in xylanase and total protein solubility, a fractionated precipitation using ethanol can be performed, since with 40% ethanol,
49% of the total protein was precipitated and more than 95% of the enzyme was kept in solution. On the other hand approx 100%
of the xylanases were recovered by precipitation after adding 80% ethanol. 相似文献
16.
17.
The possibility of modifying the Dreywood anthrone method for spectrophotometric determination of carbohydrates in order to
increase the accuracy and reproducibility of the results was examined. The classical method and a developed modification were
compared. The relative uncertainty in a determination by the modified method was less than 4%.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 218–220, May–June, 2006. 相似文献
18.
Ohne Zusammenfassung 相似文献
19.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1976,32(4):843-849
The Raman tensors for the 9 internal vibrations of Na2SO4(V) (Thenardit) crystal have been computed using the Raman tensor transfer technique. The relative intensities derived from the computed tensors are in good agreement with the experimental values measured on an oriented single crystal. It means that the Raman tensors of the unperturbed sulfate groups (Td symmetry) can be transfered to the Na2SO4(V) crystal (D2h24 symmetry) in the zero order approximation. Due to the particular orientation of SO42− in the crystal, the structure of the Na2So4 (V) is very suitable for a illustration of the computational steps of the Raman tensor transfer technique, which have been developed here in detail. 相似文献