共查询到20条相似文献,搜索用时 31 毫秒
1.
Jelena Miladinović Rozalija Ninković Milica Todorović Joseph A. Rard 《Journal of solution chemistry》2008,37(3):307-329
Isopiestic vapor-pressure measurements were made for {yMgCl2+(1−y)MgSO4}(aq) solutions with MgCl2 ionic strength fractions of y=(0,0.1997,0.3989,0.5992,0.8008, and 1) at the temperature 298.15 K, using KCl(aq) as the reference standard. These measurements
for the mixtures cover the ionic strength range I=0.9794 to 9.4318 mol⋅kg−1. In addition, isopiestic measurements were made with NaCl(aq) as reference standard for mixtures of {xNa2SO4+(1−x)MgSO4}(aq) with the molality fraction x=0.5000 that correspond to solutions of the evaporite mineral bloedite (astrakanite), Na2Mg(SO4)2⋅4H2O(cr). The total molalities, m
T=m(Na2SO4)+m(MgSO4), range from m
T=1.4479 to 4.4312 mol⋅kg−1 (I=5.0677 to 15.509 mol⋅kg−1), where the uppermost concentration is the highest oversaturation molality that could be achieved by isothermal evaporation
of the solvent at 298.15 K. The parameters of an extended ion-interaction (Pitzer) model for MgCl2(aq) at 298.15 K, which were required for an analysis of the {yMgCl2+(1−y)MgSO4}(aq) mixture results, were evaluated up to I=12.075 mol⋅kg−1 from published isopiestic data together with the six new osmotic coefficients obtained in this study. Osmotic coefficients
of {yMgCl2+(1−y)MgSO4}(aq) solutions from the present study, along with critically-assessed values from previous studies, were used to evaluate
the mixing parameters of the extended ion-interaction model. 相似文献
2.
Summary A method has been developed for separation and quantitation of midecamycin A1 and related impurities by high-performance liquid chromatography with evaporative light-scattering detection (ELSD). Chromatographic
conditions included use of a Diamonsil C18 column; the mobile phase was 52:48 acetonitrile −0.2 mol L−1 ammonium formate solution (adjusted to pH 7.3 with triethylamine) at a flow rate of 1 mL min−1. The column temperature was 35°C, the shift tube temperature of the ELSD was 105°C, and the gas flow rate of the ELSD was
3.0 L min−1. The response factors of midecamycins in HPLC-ELSD were the same; the linear equation wasy=599292.44x+2868618.04,r=0.9979, the linear range was 5–80 μg,RSD=0.21–1.54%, and theLOD andLOQ were 0.36 and 1.2 μg, respectively. The method was simple, quick, and precise and could be used to determine midecamycin
and its related impurities directly. 相似文献
3.
A. I. Gubanov N. V. Kuratieva E. Yu. Filatov S. V. Korenev 《Journal of Structural Chemistry》2012,53(3):503-508
The structures of two salts [Co(NH3)6][Rh(NO2)6] (I) and [Co(NH3)6][(NO2)3Rh(μ-NO2)1+x (μ-OH)2−x Rh(NO2)3]·(2−x)(H2O), x = 0.17 (II) are solved. Single crystals of the salts are obtained by the counter diffusion method through the gel of aqueous solutions of [Co(NH3)6]Cl3 and Na3[Rh(NO2)6]. The structure of [Co(NH3)6][Rh(NO2)6] is consistent with the diffraction data for a polycrystalline sample of poorly soluble fine salt formed in the exchange reaction between aqueous solutions of [Co(NH3)6]Cl3 and Na3[Rh(NO2)6]. The structure of [Co(NH3)6][(NO2)3Rh(μ-NO2)1+x (μ-OH)2−x Rh(NO2)3]·(2−x)(H2O), x = 0.17 exhibits the stabilizing effect of a large cation in the formation of novel, unknown previously coordination ions: [(NO2)3Rh(μ-NO2)(μ-OH)2Rh(NO2)3]3− and [(NO2)3Rh(μ-NO2)2(μ-OH)Rh(NO2)3]3−. 相似文献
4.
The most stable structures of V
x
O
y
+/V
x
O
y
(x=1, 2, y=1–5) clusters and their interaction with O2 are determined by density functional calculations, the B3LYP functional with the 6-31G* basis set. The nature of the bonding
of these clusters and the interaction with O2 have been studied by topological analysis in the framework of both the atoms-in-molecules theory of Bader and the Becke–Edgecombe
electron localization function. Bond critical points are localized by means of the analysis of the electron density gradient
field, ∇ρ(r), and the electron localization function gradient field, ∇η(r). The values of the electron density properties, i.e., electron density, ρ(r), Laplacian of the electron density, ∇2ρ(r), and electron localization function, η(r), allow the nature of the bonds to be characterized, and linear correlation is found for the results obtained in both gradient
fields. Vanadium-oxygen interactions are characterized as unshared-electron interactions, and linear correlation is observed
between the electron density properties and the V–O bond length. In contrast, O2 units involve typical shared-electron interactions, as for the dioxygen molecule. Four different vanadium–oxygen interactions
are found and characterized: a molecular O2 interaction, a peroxo O2
2− interaction, a superoxo O2
− interaction and a side-on O2
− interaction.
Received: 15 October 2001 / Accepted: 30 January 2002 / Published online: 24 June 2002 相似文献
5.
Regions of existence were determined for various types of poly- and monocrystalline solid solutions (Ln3[ScyM2−y]M3O12; {Ln3−xScx}[ScyM2−y]M3O12; Ln3[LnzScyM2−y−z] M3O12; Ln=Y, Gd; M=Ga, Al) by analyzing the diagrams rVIII−rVI (rVI are weighted mean dodecahedral and octahedral radii, respectively). We found the position of congruently melting compositions
in rVIII−rVI coordinates and optimal compositions for obtaining Nd3+- and Cr3+-doped crystals. The structure of the congruently melting composition was found to be formed of “equilibrium” polyhedra, which
need not be stabilized. It is shown that a congruently melting composition, which is absent in the original matrix, may be
achieved by isomorphous substitutions at certain positions of the structure. The most probable mechanisms of formation of
poly- and monocrystalline solid solutions with garnet structure are suggested using the calculated binodal curves of decomposition.
M. V. Lomonosov Moscow Academy of Fine Chemical Technology. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 5, pp. 23–33, September–October, 1994.
Translated by O. Kharlamova 相似文献
6.
Oddvar R?yset 《Fresenius' Journal of Analytical Chemistry》1998,360(1):69-73
Three different methods for sampling and determination of nitrogen dioxide in urban air are compared: an NO/NOx-monitor and an active (pumped) and a passive sampling method. For the latter two methods, sodium iodide is used as absorbent.
For weekly averages the results from the passive sampler are within 10–20% of the results for the two other methods in the
concentration range 15–30 μg NO2/m3. The detection limit for the passive sampler is 1 μg NO2/m3 (7 days), the precision is 5% and the accuracy is estimated to 20%. The active iodide method agrees very well with the NO/NOx-monitor. Compared on 24 h basis for a period of 3 months, covering a concentration range of 5–45 μg NO2/m3, the deviation between the two methods is within 5%, and the absorption capacity of the iodide reagent is excellent as the
breakthrough is below 1%.
Received: 3 December 1996 / Revised: 11 March 1997 / Accepted: 15 March 1997 相似文献
7.
N. S. Shaligram S. K. Singh R. S. Singhal A. Pandey G. Szakacs 《Applied biochemistry and biotechnology》2009,159(2):505-520
In the present study, compactin production by Penicillium brevicompactum WA 2315 was optimized using solid-state fermentation. The initial one factor at a time approach resulted in improved compactin
production of 905 μg gds−1 compared to initial 450 μg gds−1. Subsequently, nutritional, physiological, and biological parameters were screened using fractional factorial and Box–Behnken
design. The fractional factorial design studied inoculum age, inoculum volume, pH, NaCl, NH4NO3, MgSO4, and KH2PO4. All parameters were found to be significant except pH and KH2PO4. The Box–Behnken design studied inoculum volume, inoculum age, glycerol, and NH4NO3 at three different levels. Inoculum volume (p = 0.0013) and glycerol (p = 0.0001) were significant factors with greater effect on response. The interaction effects were not significant. The validation
study using model-defined conditions resulted in an improved yield of 1,250 μg gds−1 compactin. Further improvement in yield was obtained using fed batch mode of carbon supplementation. The feeding of glycerol
(20% v/v) on day 3 resulted in further improved compactin yield of 1,406 μg gds−1. The present study demonstrates that agro-industrial residues can be successfully used for compactin production, and statistical
experiment designs provide an easy tool to improve the process conditions for secondary metabolite production. 相似文献
8.
NO Reduction Over Noble Metal Ionic Catalysts 总被引:1,自引:0,他引:1
In last 40 years, catalysis for NO
x
removal from exhaust gas has received much attention to achieve pollution free environment. CeO2 has been found to play a major role in the area of exhaust catalysis due to its unique redox properties. In last several
years, we have been exploring an entirely new approach of dispersing noble metal ions in CeO2 and TiO2 for redox catalysis. We have extensively studied Ce1−x
M
x
O2−δ (M = Pd, Pt, Rh), Ce1−x−y
A
x
M
y
O2−δ (A = Ti, Zr, Sn, Fe; M = Pd, Pt) and Ti1−x
M
x
O2−δ (M = Pd, Pt, Rh, Ru) catalysts for exhaust catalysis especially NO reduction and CO oxidation, structure–property relation
and mechanism of catalytic reactions. In these catalysts, lower valent noble metal ion substitution in CeO2 and TiO2 creates noble metal ionic sites and oxide ion vacancy. NO gets molecularly adsorbed on noble metal ion site and dissociatively
adsorbed on oxide ion vacancy site. Dissociative chemisorption of NO on oxide ion vacancy leads to preferential conversion
of NO to N2 instead of N2O over these catalysts. It has been demonstrated that these new generation noble metal ionic catalysts (NMIC) are much more
catalytically active than conventional nano crystalline noble metal catalysts especially for NO reduction. 相似文献
9.
T. V. Maltseva E. O. Kudelko V. N. Belyakov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(13):2336-2339
It was studied the equilibrium adsorption and adsorption kinetics of Cu(II), Cd(II), Pb(II), and Cr(VI) by composite hydroxides
formed by Me
x
O
y
· nH2O and Me0.4–0.7Al0.6–0.3O
y
· nH2O, where Me = Zr, Sn and Ti. It was estimated the values of the diffusion coefficients of adsorbed ions Cu(II) and Cr(VI)
from kinetic values. It was established that the estimated diffusion coefficients of adsorbed ions Cu(II) are in the range
0.4 × 10−12–2.5 × 10−12 m2/s for individual hydroxides and 1.2 × 10−12–2.8 × 10−12 m2/s for double hydroxides. The obtained values of diffusion coefficients Cr (VI) for double hydroxides are 0.1 × 10−10–0.4 × 10−10 m2/s. 相似文献
10.
Chi Won Kim Jungmin Ahn Sung Min Kim Tae Hwan Noh Ok-Sang Jung 《Transition Metal Chemistry》2011,36(5):545-551
Type studies on competitive polyatomic anion versus acetonitrile coordination in the self-assembly of a series of [Ag2(X)
m
(bip)(NCCH3)
n
](X)2−m
(X− = NO3
−, CF3SO3
−, ClO4
−, BF4
−, and PF6
−; m = 0, 2; n = 0, 2, 4; bip = 1,4-bis(2-isonicotinoyloxyethyl)piperazine) were carried out. Each bip spacer acts as an N4 tetradentate ligand and is linked to four silver(I) centers through two pyridine and two piperazine moieties, producing a
double strand consisting of two 20-membered ring units. The coordinating environment around the silver(I) center is subtly
determined by the competition of the polyatomic anions with acetonitrile, that is, by the Ag···NCCH3 versus Ag···X interactions. The coordinating ability of acetonitrile is inversely proportional to the order of the coordination
ability of the Hoffmeister series of polyatomic anions, NO3
− ≫ CF3SO3
− > ClO4
− > BF4
− ≫ PF6
−. 相似文献
11.
A stability-indicating reversed-phase liquid chromatographic (RPLC) method has been established for analysis of ramipril (RAM)
and moexipril hydrochloride (MOEX.HCl) in the presence of the degradation products generated in studies of forced decomposition.
The drug substances were subjected to stress by hydrolysis (0.1 m NaOH and 0.1 m HCl), oxidation (30% H2O2), photolysis (254 nm), and thermal treatment (80 °C). The drugs were degraded under basic and acidic conditions and by thermal
treatment but were stable under other stress conditions investigated. Successful separation of the drugs from the degradation
products was achieved on a cyanopropyl column with 40:60 (v/v) aqueous 0.01 m ammonium acetate buffer (pH 6)–methanol as mobile phase at a flow rate of 1 mL min−1. Detection was by UV absorption at 210 nm. Response was a linear function of concentration over the range 5–50 μg mL−1 (r > 0.9995), with limits of detection and quantitation (LOD and LOQ) of 0.04 and 0.09 μg mL−1, respectively, for RAM and 0.014 and 0.32 μg mL−1, respectively, for moexipril. The method was validated for specificity, selectivity, solution stability, accuracy, and precision.
Statistical analysis proved the method enabled reproducible and selective quantification of RAM and MOEX as the bulk drug
and in pharmaceutical preparations. Because the method effectively separates the drugs from their degradation products, it
can be used as stability-indicating. 相似文献
12.
V. N. Viter 《Russian Journal of Applied Chemistry》2009,82(12):2093-2097
Substitutional solid solutions (Cu1−y
Zn
y
)2(OH)PO4·xH2O (0 ≤ y ⩽ 0.26, x = 0.1−0.2), (Cu1−y
Co
y
)2(OH)PO4·xH2O (0 ≤ y ≤ 0.10, x = 0.1−0.2), and (Cu1−y
Ni
y
)2(OH)PO4·xH2O (0 ≤ y ≤ 0.08, x = 0.1−0.2) were synthesized. The unit cell parameters of the resulting phosphates were determined, and their IR absorption
spectra were measured. The reactants were H3PO4 and mixtures of hydrous carbonates of the appropriate metals. Thermolysis
of the solid solutions was examined with (Cu1−y
Co
y
)2(OH)PO4·xH2O (0 ≤ y ≤ 0.10, x = 0.1−0.2) as an example. 相似文献
13.
B. Tong Z. C. Tan Q. Shi Y. S. Li S. X. Wang 《Journal of Thermal Analysis and Calorimetry》2008,91(2):463-469
The low-temperature heat capacity C
p,m of sorbitol was precisely measured in the temperature range from 80 to 390 K by means of a small sample automated adiabatic
calorimeter. A solid-liquid phase transition was found at T=369.157 K from the experimental C
p-T curve. The dependence of heat capacity on the temperature was fitted to the following polynomial equations with least square
method. In the temperature range of 80 to 355 K, C
p,m/J K−1 mol−1=170.17+157.75x+128.03x
2-146.44x
3-335.66x
4+177.71x
5+306.15x
6, x= [(T/K)−217.5]/137.5. In the temperature range of 375 to 390 K, C
p,m/J K−1 mol−1=518.13+3.2819x, x=[(T/K)-382.5]/7.5. The molar enthalpy and entropy of this transition were determined to be 30.35±0.15 kJ mol−1 and 82.22±0.41 J K−1 mol−1 respectively. The thermodynamic functions [H
T-H
298.15] and [S
T-S
298.15], were derived from the heat capacity data in the temperature range of 80 to 390 K with an interval of 5 K. DSC and TG measurements
were performed to study the thermostability of the compound. The results were in agreement with those obtained from heat capacity
measurements. 相似文献
14.
L. G. Detsuheva M. A. Fedotov L. I. Kuznetsova A. A. Vlasov V. A. Likholobov 《Russian Chemical Bulletin》1997,46(5):874-880
Unsaturated heteropolyanions (HPA) [PW11O39]7− stabilize TiIV hydroxo complexes in aqueous solutions (Ti: PW11 [PW11O39]7−⪯12, pH 1–3). Spectral studies (optical,17O and31P NMR, and IR spectra) and studies by the differential dissolution method demonstrated that TiIV hydroxo complexes are stabilized through interactions of polynuclear TiIV hydroxo cations with heteropolyanions [PW11TiO40
5− formed. Depending on the reaction conditions, hydroxo cations Ti
n−1O
x
H
y
m+ either add to oxygen atoms of the W−O−Ti bridges of the heteropolyanions to form the complex [PW11TiO40·Ti
n−1O
x
H
y
]
k−
(at [HPA]=0.01 mol L−1) or interact with TiIV of the heteropolyanions through the terminal o atom to give the polynuclear complexes [PW11O39Ti−O−Ti
n−1O
x
H
y
]q− (at [HPA]=0.2 mol L−1). When the complexes of the first type were treated with H2O2, TiIV ions added peroxo groups.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 914–920, May, 1997. 相似文献
15.
Aleksey A. Yaremchenko Vladislav V. Kharton Evgeny N. Naumovich Anneta A. Tonoyan Viktor V. Samokhval 《Journal of Solid State Electrochemistry》1998,2(5):308-314
Electrical conductivity, fluorite-type cubic unit cell volume and thermal expansion of the (Bi1−
x
Nb
x
)1−
y
Ho
y
O1.5+δ (x=0.05 and 0.08; y=0.10−0.15) and (Bi1−
x
Zr
x
)1−
y
Y
y
O1.5+δ (x=0.05 and 0.07; y=0.15) solid solutions have been found to decrease regularly with increasing dopant content. Annealing at temperatures below
900 K leads to a phase decomposition and to a sharp decrease in conductivity of the ceramics. Oxygen ion transference numbers
have been determined by the e.m.f. method and by Faradaic efficiency measurement to exceed 0.9. A new technique of studying
Faradaic efficiency has been proposed and verified using (Bi0.95Zr0.05)0.85Y0.15O1.5+δ and Zr0.90Y0.10O1.95 ceramic samples.
Received: 31 October 1997 / Accepted: 18 December 1997 相似文献
16.
A. Yu. Stroeva V. P. Gorelov V. B. Balakireva 《Russian Journal of Electrochemistry》2010,46(7):784-788
The ion and proton transfer numbers were measured by emf method in La1 − x
Sr
x
Sc1 − y
Mg
y
O3 − α (x = y = 0.01–0.20) system in reducing hydrogen-containing atmosphere in the range of temperatures from 630 to 920°C and pH2O from 0.61 to 2.65 kPa. Total ionic, proton, and oxygen conductivities of this system was measured as well. The electroconductivity
measurements were carried out vs. pO2 (from air to 10−14 Pa). 相似文献
17.
Attempts to develop new technologies of NO
x
(NO + NO2) emission reduction are still carried out all around the world. One of the relatively new approaches is the application of
ozone injection into the exhaust gas stream followed by the absorption process. Ozone is used to transform NO
x
to higher nitrogen oxides which yield nitric acid with better effectiveness. The main objective of this paper was to study
the influence of mole ratio (MR) O3/NO used in the ozonation process of NO
x
on the effectiveness of NO
x
oxidation to higher oxides. The ozonation process was carried out in a flow reactor for concentrations of nitric oxide in
the range of 1.5 × 10−5−7.7 × 10−5 mol dm−3 and varying O3/NO mole ratios. Measurements were conducted with the use of a FTIR spectrometer. The results obtained prove that for MR higher
than 1, the oxidation effectiveness of nitric oxides generally reaches 95 %, whereas for MR higher than 2, oxidation of NO
x
to higher nitrogen oxides is completed. 相似文献
18.
V. N. Krasil’nikov A. P. Shtin O. I. Gyrdasova E. V. Polyakov L. Yu. Buldakova M. Yu. Yanchenko V. M. Zainullina V. P. Zhukov 《Russian Journal of Inorganic Chemistry》2010,55(8):1184-1191
Ti1−x
V
x
O2−y
C
y
(0 ≤ x ≤ 0.10 and x = 0.50) whiskers having the anatase structure were synthesized via thermolysis of vanadium-doped titanium glycolate of composition
Ti1−x
V
x
(OCH2CH2O)2 (0 ≤ x ≤ 0.10 and x = 0.50). The starting reagents used to prepare Ti1−x
V
x
(OCH2CH2O)2 were mixtures of coprecipitated titanium and vanadyl hydroxides, which were heated in ethylene glycol at T ≤ 200°C: (1 − x)TiO(OH)2 + xVO(OH)2 + 2HOCH2CH2OH = Ti1−x
V
x
(OCH2CH2O)2 + 3H2O↑. Thermolysis of vanadium-doped titanium glycolate in various gas media over a wide range of temperatures is useful to prepare
titania samples doped with both vanadium and carbon to form a phase of the general composition Ti1 − x
V
x
O2 − y
C
y
whiskers prepared by thermolyzing Ti1 − x
V
x
(OCH2CH2O)2 in air at 450°C were found to have a high photocatalytic activity in hydroquinone oxidation in aqueous solutions irradiated
in the UV spectral range; the photocatalyst’s activity increases with increasing vanadium concentration. When hydroquinone
was irradiated in the blue, the maximal catalytic activity was discovered in a sample of composition Ti0.50V0.50O2−y
C
y
. Quantum-chemical calculations support experimental data that the double doping of titania (Ti1−x
V
x
O2−y
C
y
) enhances its photocatalytic activity compared to undoped anatase or anatase doped in one sublattice: Ti1−x
V
x
O2 and TiO2−y
C
y
. 相似文献
19.
P. Pasierb Ewa Drożdż-Cieśla R. Gajerski S. Łabuś S. Komornicki M. Rękas 《Journal of Thermal Analysis and Calorimetry》2009,96(2):475-480
The purpose of this work was to investigate the influence of titanium and yttrium dopants on chemical stability of selected
Ba(Ce1−xTix)1−yYyO3 compounds. The presented results are the part of wider research concerning the crystallographic structure, microstructure,
electrical and transport properties of these groups of materials.
Samples of Ba(Ce1−xTix)1−yYyO3 with x=0.05, 0.07, 0.10, 0.15, 0.20, 0.30 and y=0.05, 0.10, 0.20 (for x=0.05) were prepared by solid-state reaction method. Initially, differential thermal analysis (DTA) and thermogravimetry (TG)
were used for optimization of preparation conditions. Subsequently, DTA-TG-MS (mass spectrometry) techniques were applied
for evaluation of the stability of prepared materials in the presence of CO2. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) results were used to determine the phase composition,
structure and microstructure of materials and to assist the interpretation of DTA-TG-MS results.
The strong influence of Ti and Y dopants contents (x and y) on the properties was found. The introduction of Ti dopant led to the improvement of chemical stability against CO2. The lower Ti concentration the better resistance against CO2 corrosion was observed. Doping by Y had the opposite effect; the decrease of chemical stability was determined. In this case
the higher Y dopant concentration the better resistance was observed. The attempt to correlate the influence of dopant on
structure and chemical stability was also presented. 相似文献
20.
The applicability of mechanochemistry to produce uranium–lanthanoid mixed oxides is presented. Phase homogeneous uranium–cerium
solid solutions of the type Ce
x
U1−x
O2 (x = 0.3 ÷ 0.95) and polyphase systems containing La
y
U1−y
O2+x
(y = 0.12) were prepared by mechanochemical activation in air of sol–gel produced precursors. The possibility for synthesis
of urania–lanthania solid solution by mechanochemical interaction of La2O3 with sol–gel produced U (IV,VI) oxide is established. The crystal structures of the obtained oxides before and after the
mechanochemical treatment are analysed by the use of X-ray diffraction method. The size of the crystallites (8–16 nm), lattice
parameters, crystallite strains and densities of the oxides are calculated by BRASS program for Rietveld calculation. 相似文献