Standard enthalpies of formation of uranium compounds I. β-UO3 and γ-UO3

The standard enthalpy of formation of γ-UO₃ has been critically assessed; the value ?(292.5 ± 0.2) kcal_th mol^?1 is suggested.The enthalpies of solution of β-UO₃ and γ-UO₃ in 3 M H₂SO₄ have been measured and used to derive:

$\text{ΔH}{}_{\mathrm{f}}{}^{\mathrm{°}}\text{(β?}\text{UO}{}_3\text{, 298.15}\text{K}\text{) = ?(291.6 ± 0.2)}\text{kcal}{}_{\mathrm{th}}\text{mol}{}^{\mathrm{?}}$

     

Synthèse et caractérisation d'une série de titanates pérowskites isotypes de [CaCu3](Mn4)O12

A series of titanates which have perovskite-like arrangements and are isostructural with [CaCu₃](Mn₄)O₁₂ have been synthesized. The total charge of the A sites can be modified (1) by substituting the Ca²⁺ cations with monovalent ones and the tetravalent manganese cations of the B sites by a mixture of (Ti⁴⁺ + M⁵⁺) in which M = Ta, Nb, Sb, or (2) by substituting the Ca²⁺ cations by a combination of cations plus vacancies. In this case, if the total charge of the A sites is 2, one obtains compounds such as $\text{[}\text{Th}{}^{\mathrm{4+}}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{□}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{Cu}{}_3\text{](Ti}{}_4\text{)O}{}_{12}$ and $\text{[T}{}^{\mathrm{3+}}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{□}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{Cu}{}_3\text{](Ti}{}_4\text{O}{}_{12}\text{(T =}\text{rare earth}\text{)}$; on the contrary, if the charge is less than 2, then one has to compensate it by changing that of the B sites. This leads to compounds such as [□Cu₃](Ti₂M₂)O₁₂ (M = Ta, Nb, Sb).     

Nd3+, Eu3+, and Gd3+ ions as local probes in the NaxSr3−2xLnx(PO4)2 and KCaLn(PO4)2 rare earth phosphates

Use of Nd³⁺, Eu³⁺, and Gd³⁺ as local structural probes allows the determination of the rare earth positions in the Na_xSr_3?2xLn_x(PO₄)₂ (Ln = La to Tb) and KCaLn(PO₄)₂ phases (Ln = rare earth). Moreover, a common feature of both series is a particularly high splitting of the excitation ${}^6\text{P}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ and ${}^6\text{P}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ levels of the Gd³⁺ ions.     

EPR and magnetization of GdGa2

Paramagnetic resonance and magnetic measurements were performed on powdered samples of GdGa₂. The magnetic data indicated ferrimagnetic behavior with $\text{T}{}_{\mathrm{c}}\text{? 181°}\text{K}$. Above 250° K the susceptibility obeys the Curie-Weiss law $\text{χ}{}_{\mathrm{g}}\text{=}\text{2.66}{}_2\text{× 10}{}^{\mathrm{?2}}\text{(T ? 27.6)}\text{emu/g-Oe}$ which corresponds to an effective moment of 7.95 Bohr magnetons. Over the range from 190 to 300°K the data obey a Néel type law, $\text{χ}{}_{\mathrm{g}}{}^{\mathrm{?1}}\text{= 35.95 (T ? 12.5) ?}\text{2.20 × 10}{}^4\text{(T ? 177)}$, which is indicative of ferrimagnetic order. The resonance measurements were performed at 9.013 gHz at 247, 296, and 349°K. The spectra were analyzed with a computerized curve-fitting technique that involves a linear combination of Lorentzian absorption and dispersion susceptibility components. Following demagnetization corrections, the g-factor was found to be 1.983₂ while the half-power, half-linewidth was 592.7 Oersteds.     

Crystal structure,Mössbauer,and magnetic behavior of mixed valence compounds in the BaFeS system: Ba3(Ba1−xAlx)Fe2S6[S1−y(S2)y]

The compounds $\text{Ba}{}_4\text{Fe}{}_2\text{S}{}_6\text{[S}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{(}\text{S}{}_2\text{)}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{]}$ and Ba_3.6Al_0.4Fe₂S₆[S_0.6(S₂)_0.4], designated I and II, were prepared by reacting BaS, Fe, and S powders and Al foils in graphite containers sealed in evacuated quartz ampoules at approximately 1100°C. The crystal structure of I was determined using 1682 independent, nonzero X-ray reflections, while 3589 were used for II. They are triclinic, $\text{A}\text{l}$:

$\text{a=9.002(2)}\text{A}\text{?}\text{,b=6.7086(8)}\text{A}\text{?}\text{,c=24.658(4)}\text{A}\text{?}\text{α91.49(2)°,}$

$\text{β=105.10(2)°y=90.74(2)°,ψ}{}_{\mathrm{calc}}\text{=4.15g/cm}{}^3\text{,for I:}$

$\text{a=8.993(6)}\text{A}\text{?}\text{,b=6.708(7)}\text{A}\text{?}\text{,c=24.70(1)}\text{A}\text{?}\text{α91.11(6)°,}$

$\text{β=105.04(6)°y=90.90(9)°,ψ}{}_{\mathrm{calc}}\text{=3.90g/cm}{}^3\text{,for II:}$

BaS₆ trigonal prisms share edges to form distorted hexagonal rings which form one-dimensional chains leaving two free lateral edges. The chains link in a stairstep manner with the rings offset along the [301] direction. These stairsteps join in a complicated manner to form a three-dimensional network. Fe ions are in two sites forming isolated FeS₄ tetrahedra and isolated Fe₂S₆ dimers by edge-sharing tetrahedra. The Al substitution occurs in the trigonal prisms which have free edges with Al replacing Ba. Room-temperature Mössbauer isomer shifts are 0.20 mm/sec. for I and 0.30 mm/sec for II. These data indicate that upon Al substitution charge compensation occurs by reducing Fe³⁺. Valence calculations indicate that Fe in edge-sharing tetrahedra are reduced while the Fe in the isolated tetrahedron remains unchanged. The effective charge distribution in the Al substituted compound is approximately Fe³⁺, Fe^2.5+ with electron delocalization across the shared edge. Room temperature electrical resistivity is 10⁵ ohm/cm. The compositions of the crystals are best represented by the formulas $\text{[}\text{Ba}{}_4\text{Fe}{}_2\text{S}{}_7\text{]}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{·[}\text{Ba}{}_4\text{Fe}{}_2\text{S}{}_6\text{(S}{}_2\text{)]}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}$ and [Ba₃AlFe₂S₇]_0.4·[Ba₄Fe₂S₇]_0.2·[Ba₄Fe₂S₆(S₂)]_0.4. The replacement of a sulfide by a disulfide ion is thought to be strongly dependent on the sulfur activity during the preparation.     

Crystal structures of some niobium and tantalum oxides. VIII. The 5Rb2O:14.6Ta2O5 phase—A tunnel structure

Rb₁₀Ta_29.20O₇₈ crystallizes in the hexagonal system with unit-cell dimensions (from single-crystal data) a = 7.503(4)Å, c = 36.348(4)Å, and space group $\text{P6}{}_3\text{mmc}\text{, z = 1}$. The structure was solved using three-dimensional Patterson and Fourier techniques. Of the 666 unique reflections measured by counter techniques, 515 with I ? 3σ(I) were used in the least-squares refinement of the model to a conventional R of 0.057 (R_ω = 0.039). The structure of Rb₁₀Ta_29.20O₇₈ consists of layers of corner-sharing groups of six edge-shared octahedra separated by layers of single octahedra and double hexagonal tungsten bronze-like layers, these layers being perpendicular to the hexagonal c-axis. Nine-coordinate tricapped trigonal prismatic sites between the hexagonal tungsten bronze-like layers are partially occupied by Ta(V) ions.     

Thermodynamics of hydrogen trapping in intermetallic compounds: Application to LaNi5H

It has been observed for several intermetallic compound/H systems that deviations from Sieverts' law of ideal solubility occur which are in the opposite direction from the deviations from ideality which occur in pure metal/H systems. The principal source of nonideality on both types of interstitial solutions arises from the changes of the relative partial molar enthalpy of H₂ solution, ΔH_H, with H content. The variations of ΔH_H with H content are, however, in the opposite directions for intermetallic/H and pure metal/H interstitial solutions. Relative partial molar entropies for solution of H₂ in the α-phase of the $\text{LaNi}{}_5\text{H}$ system are given at 298.2 K. These have been determined from calorimetric determinations of ΔH_H and measurements of . The partial entropies show unusual extrema as a function of H content. A model based on trapping of H atoms is proposed which explains the variations of ΔH_H and ΔS_H. Since the deviations from ideality arising from an increase of ΔH_H with H content seem to be limited to solids with at least two different ordered metal components, e.g., intermetallic compounds, it seems reasonable to assign the trapping sites to interstices which result from an interchange of metal atoms. This interchange may create interstices rich in those nearest-neighbor metal atoms which have the greatest affinity for H.     

Oxysulfure de scandium Sc2O2S

Sc₂O₂S is hexagonal, $\text{P6}{}_3\text{mmc}\text{, a = 3.5196(4)}$ Å, c = 12.519(2) Å, Z = 2, Dc = 3.807 g cm^?3, Dm = 4.014 g cm^?3, μ(MoKα) = 55.51 cm^?1. The final R value is 0.038 for 205 symmetry-independent reflections. This scandium oxysulfide has c = 12.52 Å, twice the value found in rare earth oxysulfides. An La₂O₂S cell combined with its reflection in a (001) mirror gives the Sc₂O₂S cell.     

Etude cristallochimique des phases de type perovskite du systeme Th0.25 NbO3NaNbO3

The compound Th_0.25 NbO₃ melts congruently at 1390°C. Single crystals obtained by slow cooling from the melt are transparent and show uniaxial optical properties. A single-crystal X-ray analysis confirms the tetragonal cell found by Kovba and Trunov from a powder data and gives a = 3.90 Å and c = 7.85 Å. No systematic absence of the hkl reflections is observed on precession films. The relative intensities of the main reflections are characteristic of a perovskite-like arrangement ABO₃ whose large dodecahedral A sites are only partly occupied. Several domains have been found in the perovskite-type solid solution (1 ? x) Th_0.25NbO₃-x NaNbO₃. For 0 ? x ? 0.5 the phases have a tetragonal cell with $\text{a ? a}{}_0$ and $\text{c ? 2a}{}_0$ as in pure Th_0.25 NbO₃. When 0.6 ? x ? 0.8 the corresponding phases crystallize with a small cubic cell ($\text{a}{}_0\text{? 3.9}$Å), while phases with 0.9 ? x ? 1 have an orthorhombic cell ($\text{a ? 2}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{a}{}_0\text{, b ? 2}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{a}{}_0\text{, c ? a}{}_0$).     

Nonstoichiometry and defect structure of the perovskite-type oxides La1−xSrxFeO3−°

In order to elucidate the defect structure of the perovskite-type oxide solid solution La_1?xSr_xFeO_3?δ (x = 0.0, 0.1, 0.25, 0.4, and 0.6), the nonstoichiometry, δ, was measured as a function of oxygen partial pressure, P_O2, at temperatures up to 1200°C by means of the thermogravimetric method. Below 200°C and in an atmosphere of P_O2 ≥ 0.13 atm, δ in La_1?xSr_xFeO_3?δ was found to be close to 0. With decreasing log P_O2, δ increased and asymptotically reached $\text{x}\text{2}$. The value corresponding to $\text{δ =}\text{x}\text{2}$ was about ?10 at 1000°C. With further decrease in log P_O2, δ slightly increased. For LaFeO_3?δ, the observed δ values were as small as <0.015. It was found that the relation between δ and log P_O2 is interpreted on the basis of the defect equilibrium among Sr′_La (or V?_La for the case of LaFeO_3?δ), V^··_O, Fe′_Fe, and Fe^·_Fe. Calculations were made for the equilibrium constants K_ox of the reaction

$\text{1}\text{2}\text{O}{}_2\text{(g) + V}{}^{\mathrm{··}}{}_{\mathrm{o}}\text{+ 2Fe}{}^{\mathrm{x}}{}_{\mathrm{Fe}}\text{= O}{}^{\mathrm{x}}{}_{\mathrm{o}}\text{+ 2Fe}{}^{\mathrm{·}}{}_{\mathrm{Fe}}$

and K_i for the reaction

$\text{2Fe}{}^{\mathrm{x}}{}_{\mathrm{Fe}}\text{= Fe}{}^{\mathrm{\prime }}{}_{\mathrm{Fe}}\text{+ Fe}{}^{\mathrm{·}}{}_{\mathrm{Fe·}}$

Using these constants, the defect concentrations were calculated as functions of P_O2, temperature, and composition x. The present results are discussed with respect to previously reported results of conductivity measurements.     

Etude comparative des structures type K4NiF4 et pérovskite par la méthode des invariants

The study of K₂NiF₄ and perovskite structure type by the “method of invariants” leads to the relationship: $\text{(A-X)}{}_9\text{2}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{? (A-X)}{}_{12}\text{=}\text{constant}$, where (A-X)₉ and (A-X)₁₂ are the invariant values associated with cation A in coordination number 9 and 12. In the case where A = K⁺ and X = F^?, we propose the relationship:

$\text{(K}{}^{\mathrm{+}}\text{?F)}{}_{\mathrm{R}}\text{= 2.832 R}{}^{\mathrm{<mtext>1</mtext><mtext>11.4</mtext>}}$

where R is the coordination number.     

Laser-molecular beam measurement of hyperfine structure in the I2 spectrum

Very high resolution measurements of hyperfine structure on the P(13) and R(15), 43?0, $\text{3}{}_{\mathrm{gp}}{}_0{}^{\mathrm{+}}{}_{\mathrm{u}}\text{←}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ transitions in iodine 127 were made using laser molecular beam spectroscopy. The observed linewidth was 300 kHz (fwhm) giving a resolution of 5 × 10^?10 The observed spectrum was fitted to obtain a quadrupole coupling strength difference of ΔeQq = 1906 ± 2 MHz and a spin rotation interaction strength difference of ΔC_I = 181 ± 7 kHz between the upper and lower levels of the P(13) transition. For the R (15) transition ΔeQq = 1905 ± 2 MHz and ΔC_I = 167 ± 5 kHz.     

Heat capacity and thermodynamic functions of CsCrCl3 and RbCrCl3. Structural phase transitions

We present the heat capacities measured by adiabatic calorimetry from 6 to 350 K, and by differential scanning calorimetry from 300 to 500 K, of CsCrCl₃ and RbCrCl₃. A first-order transition at T_c = (171.1±0.1) K was detected for CsCrCl₃. The RbCrCl₃ showed at T_c = (193.3±0.1) K a transition with thermal hysteresis at temperatures just below the maximum. At T₁ = (440±10) K a continuous transition was also detected. Furthermore, at T_N ≈ 16 K, and for both compounds, a small bump due to magnetic long-range ordering was observed. The thermodynamic functions at 298.15 K are

     

14.

Low-temperature luminescence of Eu³⁺ in K₂EuCl₅     

Harry G. Brittain  Gerd Meyer 《Journal of solid state chemistry》1984,54(2):156-163

The luminescence associated with the Eu³⁺ ion in K₂EuCl₅ has been studied at cryogenic temperatures under conditions of high resolution. Emission was observed to originate from both the ⁵D₀ and ⁵D₁ excited states, and transitions to the ${}^7\text{F}{}_0\text{,}{}^7\text{F}{}_1\text{,}{}^7\text{F}{}_2\text{,}{}^7\text{F}{}_3$, and ⁷F₄ ground levels were observed. The fine structure observed within these emission bands was found to be consistent with the existence of an effective C₄ site symmetry for the emitting Eu(III) species, even though the crystal structure does not indicate the presence of a true or pseudo C₄ axis.     

15.

NMR study of hydrogen molybdenum bronzes: H_1.71MoO₃ and H_0.36MoO₃     

R.C.T. Slade  T.K. Halstead  P.G. Dickens 《Journal of solid state chemistry》1980,34(2):183-192

Proton NMR relaxation times (T₂T₁, and T_1?) and absorption spectra are reported for the compounds H_1.71MoO₃ (red monoclinic) and H_0.36MoO₃ (blue orthorhombic) in the temperature range 77 K < T < 450 K. Rigid lattice dipolar spectra show that both compounds contain proton pairs, as OH₂ groups coordinated to Mo atoms in H_1.71MoO₃ and as pairs of OH groups in H_0.36MoO₃. The room temperature lineshape for H_1.71MoO₃ shows that the average chemical shielding tensor has a total anisotropy of 20.1 ppm. The relaxation measurements confirm that hydrogen diffusion occurs and give E_A = 22 kJ mole^?1 and $\text{τ}{}^0{}_{\mathrm{<mtext>C</mtext>}}\text{? 10}{}^{\mathrm{?13}}\text{sec}$ for H_1.71MoO₃ and E_A = 11 kJ mole^?1 and $\text{τ}{}^0{}_{\mathrm{<mtext>C</mtext>}}\text{? 3 × 10}{}^{\mathrm{?8}}\text{sec}$ for H_0.36MoO₃.     

16.

Mutual solubility of n-butanol + water under high pressures     

Yasuhiro Aoki  Takashi Moriyoshi 《The Journal of chemical thermodynamics》1978,10(12):1173-1179

The mutual solubilities of {xCH₃CH₂CH₂CH₂OH+(1-x)H₂O} have been determined over the temperature range 302.95 to 397.75 K at pressures up to 2450 atm. An increase in temperature and pressure results in a contraction of the immiscibility region. The results obtained for the critical solution properties are: T_o(U.C.S.T.) = 397.85 K and x_o = 0.110 at 1 atm; $\text{(}\text{dT}{}_{\mathrm{o}}\text{d}\text{p}\text{) = ?(12.0±0.5)×10}{}^{\mathrm{?3}}\text{K atm}{}^{\mathrm{?1}}$ at p < 400 atm and $\text{(}\text{dT}{}_{\mathrm{o}}\text{d}\text{p}\text{) = ?(7.0±0.7)×10}{}^{\mathrm{?3}}\text{K atm}{}^{\mathrm{?1}}$ at 800 atm < p < 2500 atm; $\text{(}\text{dx}{}_{\mathrm{o}}\text{d}\text{T}\text{) = ?(4.0±0.5)×10}{}^{\mathrm{?4}}\text{K}{}^{\mathrm{?1}}$.     

17.

Valence state of the Fe ions in Sr_1−yLa_yFeO₃     

M. Takano  J. Kawachi  N. Nakanishi  Y. Takeda 《Journal of solid state chemistry》1981,39(1):75-84

The Sr²⁺_1?yLa³⁺_yFeO₃ system with 0.1 ≦ y ≦ 0.6 has been studied mainly by the Mössbauer effect. The results are discussed referring to the Ca_1?xSr_xFeO₃ system. The following four kinds of electronic phases have been observed: the paramagnetic and the antiferromagnetic average valence phases and the corresponding mixed valence phases. Two kinds of Fe ions coexist, in general, in the mixed valence phases. In the antiferromagnetic mixed valence phase, typically at 4 K, the magnetic hyperfine field and the center shift each takes a wide range of value depending on the composition, while a beautiful correlation is kept between them. The extreme values are close to those expected for Fe³⁺ and Fe⁵⁺. The appropriate chemical formulas are, therefore, Ca_1?xSr_xFe^(3+Δ)+_0.5Fe^(5?Δ)+_0.5O₃ and $\text{Sr}{}_{\mathrm{1?y}}\text{La}{}_{\mathrm{y}}\text{Fe}{}^{\mathrm{(3+\delta )+}}{}_{\mathrm{<mtext>(1+y)</mtext><mtext>2</mtext>}}\text{Fe}{}^{\mathrm{(5?\delta )+}}{}_{\mathrm{<mtext>(1?y)</mtext><mtext>2</mtext>}}\text{O}{}_3$.     

18.

Solid solubility of Ge,Si, and Mg in Fe₂O₃ and photoelectric behavior     

H.L. Sanchez  H. Steinfink  H.S. White 《Journal of solid state chemistry》1982,41(1):90-96

Solid solutions of GeO₂ in Fe₂O₃ were prepared by mechanically mixing the solids and firing at 1000°C in air, and from a gel obtained by the addition of an alcohol solution of germanium ethoxide to iron dissolved in HNO₃. The dried gel was then heated at 1000°C. The solubility limit is 5 mole% GeO₂, Fe_1.95Ge_0.05O₃. Similar procedures were used to prepare solid solutions with Si and the solubility limit is greater than 4 mole% SiO₂. Firing of mixtures or gels of Fe₂O₃ containing Mg produces a spinel phase even at the lowest detectable concentrations. The resistivity of pressed pellets of Fe_2?xGe_xO₃ varies from about 10⁶ ohm-cm for x = 0 to about 10^?1 ohm-cm for x = 0.05. The photoassisted electrolysis of water at Ge-doped Fe₂O₃ electrodes is demonstrated. The $\text{Fe}{}_2\text{O}{}_3\text{(Ge)}\text{0.7 M}\text{Fe(CN)}{}^{\mathrm{4?}}{}_6\text{,}\text{0.05 M}\text{Fe(CN)}{}^{\mathrm{3?}}{}_6\text{Pt}$ photoelectrochemical cell showed a 0.29-V open-circuit voltage, 1.2-mA/cm² short-circuit current, 0.31 fill factor, and 0.06% power efficiency.     

19.

Verbesserte endpunktsbestimmung in der potentiometrischen analyse     

F.L. Hahn 《Analytica chimica acta》1954

If in a potentiometric titration each addition of reagent equals Δv and if the observed potential steps are, in decreasing order, Δ^E_m, Δ^E₁ and Δ^E₂, the ratio ρ_α = $\text{Δ}{}^{\mathrm{E}}{}_2\text{2Δ}{}^{\mathrm{E}}{}_1$is formed; ρ_αΔv is the difference between the equivalence point and the known volume of reagent next to it. Both an extraordinary increase in the precision and a valuable simplification of the analysis are obtained. For Q = $\text{Δ}{}^{\mathrm{E}}{}_{\mathrm{m}}\text{Δ}{}^{\mathrm{E}}{}_1$ < 2.5 or ρ_α < 0.25 this value is approximated; but in this case a new series with doubled intervals may be formed from the potential steps observed in which ρ_α is very near to 0.5, found hence absolutely accurate.     

20.

Electrical conductivity of Th₃P₄-type EnLn₂S₄     

Mineo Sato  Gin-Ya Adachi  Jiro Shiokawa 《Journal of solid state chemistry》1980,31(3):337-341

Electrical conductivity measurements of Th₃P₄-type EuLn₂S₄ (Ln = LaGd) compounds have been made as functions of temperature and sulfur vapor pressure. These compounds are all p-type semiconductors, and their conductivities at room temperature have almost the same values for the specimens from EuLa₂S₄ to EuNd₂S₄ but increase on going from EnNd₂S₄ to EuGd₂S₄. In addition, the conductivity of EuGd₂S₄ is sensitive to sulfur vapor pressure and obeys the relationship . The mechanism of electrical transport in these compounds is discussed.     

	$\text{C}{}_{\mathrm{<mtext>p,</mtext><mtext>m</mtext>}}\text{R}$	$\text{S}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{R}$	$\text{{H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(T)?H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(0)}}\text{R}\text{K}$	$\text{?{G}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(T)?H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(0}}\text{RT}$
CsCrCl3	15.38	26.49	3503.2	14.735
RbCrCl3	15.76	25.99	3556.8	14.384

Low-temperature luminescence of Eu3+ in K2EuCl5

The luminescence associated with the Eu³⁺ ion in K₂EuCl₅ has been studied at cryogenic temperatures under conditions of high resolution. Emission was observed to originate from both the ⁵D₀ and ⁵D₁ excited states, and transitions to the ${}^7\text{F}{}_0\text{,}{}^7\text{F}{}_1\text{,}{}^7\text{F}{}_2\text{,}{}^7\text{F}{}_3$, and ⁷F₄ ground levels were observed. The fine structure observed within these emission bands was found to be consistent with the existence of an effective C₄ site symmetry for the emitting Eu(III) species, even though the crystal structure does not indicate the presence of a true or pseudo C₄ axis.     

NMR study of hydrogen molybdenum bronzes: H1.71MoO3 and H0.36MoO3

Proton NMR relaxation times (T₂T₁, and T_1?) and absorption spectra are reported for the compounds H_1.71MoO₃ (red monoclinic) and H_0.36MoO₃ (blue orthorhombic) in the temperature range 77 K < T < 450 K. Rigid lattice dipolar spectra show that both compounds contain proton pairs, as OH₂ groups coordinated to Mo atoms in H_1.71MoO₃ and as pairs of OH groups in H_0.36MoO₃. The room temperature lineshape for H_1.71MoO₃ shows that the average chemical shielding tensor has a total anisotropy of 20.1 ppm. The relaxation measurements confirm that hydrogen diffusion occurs and give E_A = 22 kJ mole^?1 and $\text{τ}{}^0{}_{\mathrm{<mtext>C</mtext>}}\text{? 10}{}^{\mathrm{?13}}\text{sec}$ for H_1.71MoO₃ and E_A = 11 kJ mole^?1 and $\text{τ}{}^0{}_{\mathrm{<mtext>C</mtext>}}\text{? 3 × 10}{}^{\mathrm{?8}}\text{sec}$ for H_0.36MoO₃.     

Mutual solubility of n-butanol + water under high pressures

The mutual solubilities of {xCH₃CH₂CH₂CH₂OH+(1-x)H₂O} have been determined over the temperature range 302.95 to 397.75 K at pressures up to 2450 atm. An increase in temperature and pressure results in a contraction of the immiscibility region. The results obtained for the critical solution properties are: T_o(U.C.S.T.) = 397.85 K and x_o = 0.110 at 1 atm; $\text{(}\text{dT}{}_{\mathrm{o}}\text{d}\text{p}\text{) = ?(12.0±0.5)×10}{}^{\mathrm{?3}}\text{K atm}{}^{\mathrm{?1}}$ at p < 400 atm and $\text{(}\text{dT}{}_{\mathrm{o}}\text{d}\text{p}\text{) = ?(7.0±0.7)×10}{}^{\mathrm{?3}}\text{K atm}{}^{\mathrm{?1}}$ at 800 atm < p < 2500 atm; $\text{(}\text{dx}{}_{\mathrm{o}}\text{d}\text{T}\text{) = ?(4.0±0.5)×10}{}^{\mathrm{?4}}\text{K}{}^{\mathrm{?1}}$.     

Valence state of the Fe ions in Sr1−yLayFeO3

The Sr²⁺_1?yLa³⁺_yFeO₃ system with 0.1 ≦ y ≦ 0.6 has been studied mainly by the Mössbauer effect. The results are discussed referring to the Ca_1?xSr_xFeO₃ system. The following four kinds of electronic phases have been observed: the paramagnetic and the antiferromagnetic average valence phases and the corresponding mixed valence phases. Two kinds of Fe ions coexist, in general, in the mixed valence phases. In the antiferromagnetic mixed valence phase, typically at 4 K, the magnetic hyperfine field and the center shift each takes a wide range of value depending on the composition, while a beautiful correlation is kept between them. The extreme values are close to those expected for Fe³⁺ and Fe⁵⁺. The appropriate chemical formulas are, therefore, Ca_1?xSr_xFe^(3+Δ)+_0.5Fe^(5?Δ)+_0.5O₃ and $\text{Sr}{}_{\mathrm{1?y}}\text{La}{}_{\mathrm{y}}\text{Fe}{}^{\mathrm{(3+\delta )+}}{}_{\mathrm{<mtext>(1+y)</mtext><mtext>2</mtext>}}\text{Fe}{}^{\mathrm{(5?\delta )+}}{}_{\mathrm{<mtext>(1?y)</mtext><mtext>2</mtext>}}\text{O}{}_3$.     

Solid solubility of Ge,Si, and Mg in Fe2O3 and photoelectric behavior

Solid solutions of GeO₂ in Fe₂O₃ were prepared by mechanically mixing the solids and firing at 1000°C in air, and from a gel obtained by the addition of an alcohol solution of germanium ethoxide to iron dissolved in HNO₃. The dried gel was then heated at 1000°C. The solubility limit is 5 mole% GeO₂, Fe_1.95Ge_0.05O₃. Similar procedures were used to prepare solid solutions with Si and the solubility limit is greater than 4 mole% SiO₂. Firing of mixtures or gels of Fe₂O₃ containing Mg produces a spinel phase even at the lowest detectable concentrations. The resistivity of pressed pellets of Fe_2?xGe_xO₃ varies from about 10⁶ ohm-cm for x = 0 to about 10^?1 ohm-cm for x = 0.05. The photoassisted electrolysis of water at Ge-doped Fe₂O₃ electrodes is demonstrated. The $\text{Fe}{}_2\text{O}{}_3\text{(Ge)}\text{0.7 M}\text{Fe(CN)}{}^{\mathrm{4?}}{}_6\text{,}\text{0.05 M}\text{Fe(CN)}{}^{\mathrm{3?}}{}_6\text{Pt}$ photoelectrochemical cell showed a 0.29-V open-circuit voltage, 1.2-mA/cm² short-circuit current, 0.31 fill factor, and 0.06% power efficiency.     

Verbesserte endpunktsbestimmung in der potentiometrischen analyse

If in a potentiometric titration each addition of reagent equals Δv and if the observed potential steps are, in decreasing order, Δ^E_m, Δ^E₁ and Δ^E₂, the ratio ρ_α = $\text{Δ}{}^{\mathrm{E}}{}_2\text{2Δ}{}^{\mathrm{E}}{}_1$is formed; ρ_αΔv is the difference between the equivalence point and the known volume of reagent next to it. Both an extraordinary increase in the precision and a valuable simplification of the analysis are obtained. For Q = $\text{Δ}{}^{\mathrm{E}}{}_{\mathrm{m}}\text{Δ}{}^{\mathrm{E}}{}_1$ < 2.5 or ρ_α < 0.25 this value is approximated; but in this case a new series with doubled intervals may be formed from the potential steps observed in which ρ_α is very near to 0.5, found hence absolutely accurate.     

Electrical conductivity of Th3P4-type EnLn2S4

Electrical conductivity measurements of Th₃P₄-type EuLn₂S₄ (Ln = LaGd) compounds have been made as functions of temperature and sulfur vapor pressure. These compounds are all p-type semiconductors, and their conductivities at room temperature have almost the same values for the specimens from EuLa₂S₄ to EuNd₂S₄ but increase on going from EnNd₂S₄ to EuGd₂S₄. In addition, the conductivity of EuGd₂S₄ is sensitive to sulfur vapor pressure and obeys the relationship . The mechanism of electrical transport in these compounds is discussed.