Composition and properties of polysaccharides from rice husk

The composition and content of polysaccharides obtained from different samples of rice husk by successive treatment with water, ammonium oxalate (or oxalic acid), and alkali were studied. The chemical composition of the rice husk residues after the extraction was examined, and the possibility of their use for preparing amorphous silica or cellulose-containing products, depending on the hydrolysis conditions, was assessed.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 11, 2004, pp. 1901–1904.Original Russian Text Copyright © 2004 by Zemnukhova, Tomshich, Mamontova, Komandrova, Fedorishcheva, Sergienko.     

Complexation processes in KF-SbF<Subscript>3</Subscript>-H<Subscript>2</Subscript>O system studied by calorimetric titration

Complexation in a KF-SbF₃-H₂O system is studied in a range of molar ratios of fluorides KF : SbF₃= (0.1–2) : 1 by calorimetric titration. The equilibrium formation constants of complexes KSb₂F₇, KSbF₄, and K₂SbF₅ (5.8×10⁵±800, 3.3×10⁴±500, and 1.9×10⁶± 950, respectively) and the changes in enthalpy (–31.75± 0.74, –28.15±0.44, and –25.5±0.64 J mol^–1, respectively) and entropy (4±7, –8±5, and –35±9 J mol^–1 K^–1, respectively) are determined. The thermodynamic stability of the antimony(III) fluoride complexes is found to increase on going from KSb₂F₇ to K₂SbF₅.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 3, 2005, pp. 168–171.Original Russian Text Copyright © 2005 by Kovaleva, Zemnukhova, Lebedeva, Fedorishcheva.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date.     

Study of isomorphism in fluorine-containing antimony(III) complexes

The mutual influence of the atoms on the composition of solid fluorine-containing antimony(iii) complexes formed in aqueous solutions in the (MF) _x −(M′F) _n−x −SbF₃ (M, M′=Na, K, Rb, Cs, and NH₄;n=1, 2;x=0 to 2), (KNO₂) _n −(KY) _n −SbF₃ (Y=F, Cl, SO₄;n=0.5, 1), and K₂SbF₅−K₂SbCl₅ systems was investigated by elemental, X-ray, and thermogravimetric analyses and by IR and^121,123Sb NQR spectroscopy. The isomorphism conditions for fluorine-containing antimony(iii) compounds resulting in the formation of complexes NaM′SbF₅·1.5H₂O (M′=K and Rb), K₂SbF₅·1.5H₂O, NaCs₃Sb₄F₁₆·H₂O, KsbF₃Cl, K₂SbF₂Cl₃ with constant compositions, continuous M _x M′_2−x SbF₅ (0<x<2) and limited M _x M′_1−x SbF₄ (0.25<x<0.75; M, M′=K, Rb, Cs, and NH₄) solid solutions or LiF+MSbF₄ (M=Na, K, Rb, and Cs), M₂SbF₅+Cs₂SbF₅ (M=Na and K) and MSbF₄+NaSbF₄ (M=Rb and NH₄) mechanical mixtures were determined. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 103–108, January, 1999.     

Products of the catalytic liquid-phase oxidation of 3-carene

The liquid-phase oxidation of 3-carene in the presence of various catalytic systems has been studied. The possibility has been shown of the directed preparation of 3-carene oxide, of ketones with a carane skeleton and a 7-membered ring, or of aromatic tertiary alcohols.Institute of Physical Organic Chemistry, Academy of Sciences of the Belorussian SSR, Minsk. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 328–334, May–June, 1991.     

Synthesis and crystal structure of new sodium oxothiocyanofluoroantimonate(III) Na2Sb5F9O3(NCS)2

Na₂Sb₅F₉O₃(NCS)₂, a new complex, has been synthesized from NaSCN and SbF₃ aqueous solutions and studied by chemical, X-ray diffraction, and thermal analyses and IR, ^121,123Sb NQR, and ¹⁹F NMR spectroscopy. Its layered structure (triclinic symmetry system, a = 6.9998(1) Å, b = 9.4180(1) Å, c = 13.1094(2) Å, α = 74.815(1)°, β = 78.188(1)°, γ = 82.779(1)°, Z = 2, space group P $\bar 1$ ) is built of Na⁺ cations and [Sb₁₀F₁₈O₆(NCS)₄]^4? decanuclear complex anions that consist of two [Sb₅F₉O₃(NCS)₂]^2? pentanuclear complex anions linked by two weak Sb-F ionic bonds (2.529(2) Å). Decanuclear complex anions are linked into layers by secondary Sb…F bonds and Na-F bonds. Van der Waals interactions link these layers into a framework. The complex is stable up to 200°C.     

Structure and phase composition of the intermetallide Ni3Al+0.5 at.% B synthesized under pressure

We have used x-ray structural analysis, together with transmission and scanning electron microscopy, to study the phase composition, structure, and elemental distribution in the intermetallide Ni₃Al+0.5 at.% B, produced by self-propagating high-temperature synthesis under pressure. It is shown that the synthesized material is an ordered alloy of the type L1₂. The phase composition of the alloy Ni₃Al+0.5 at.% B is represented by the phases Ni₃Al (the fundamental phase), grains of a layered NiAl composition, and inclusions of Ni₃B. The latter is found inside the Ni₃Al grains, in the form of surrounded particles, and at dislocations and at grain boundaries in the NiAl phase. Institute for the Physics of Strength and Materials Production. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 59–64, September, 1996.     

Conditions for the synthesis of Sb(III) fluoride complexes

Complexation of Sb(III) fluorides with alkali metal, ammonium, and thallium cations in the MF-SbF₃-H₂O systems at the molar ratios MF : SbF₃=(0.01–2) : 1 is studied by preparative chemistry, pH-metry, ₁₉F NMR, IR and X-ray powder diffraction methods. The crystals of Sb₃O₂F₅, MSb₄F₁₃, MSb₃F₁₀, MSb₂F₇, M₂Sb₃F₁₁, M₃Sb₄F₁₅, MSbF₄, M₂SbF₅ are synthesized and the factors influencing their formation are discussed. Some types of Sb(III) fluoride complexes are shown to be formed in the MX-SbF₃-H₂O systems (X = Cl^–, NO₃^–, BF₄^–, SCN^–, ClO₄^–).Translated from Koordinatsionnaya Khimiya, Vol. 30, No. 12, 2004, pp. 833–837.Original Russian Text Copyright © 2004 by Zemnukhova, Kovaleva, Fedorishcheva, Konshin, Davidovich.     

Variations of the shape of123Sb NQR tines in phase transitions in K2SbF5

Variations of the shape of¹²³Sb NQR lines in phase transitions in a new ionic conductor, potassium pentafluoroantimonite(ui), in the temperature range from 77 to 430 K were studied. The transition from a paraelectric phase to a commensurate phase occurs via incommensurate and commensurate-modulated phases.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2497–2500, October, 1996.     

121,123Sb NQR investigation of chlorofluoroantimonates(III) M2SbCl3F2 (M = Rb. Cs,and NH4)

Antimony(m) chlorofluoride complexes M₂SbCl₃F₂ (M = Rb, Cs, or NH₄) were studied by the^121,123Sb NQR method. A temperature range (77–285 K) with anomalous change in the NQR parameters and a second-order phase transition at 250–280 K for (NH₄)₂SbCl₃F₂ were found.Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 382–385, February, 1996     

Antimony(III) Oxofluorides α-Sb3O2F5 and β-Sb3O2F5: Synthesis and Crystal Structures

The conditions for the synthesis of two polymorphous forms of antimony(III) oxofluoride Sb₃O₂F₅ from aqueous solutions are established. The crystal structure of a new polymorphous modification -Sb₃O₂F₅ is determined (monoclinic crystals with a = 6.9548(6) Å, b = 9.1043(7) Å, c = 20.336(2) Å, = 94.167(2)°, V = 1284.2(2) ų, Z = 8, (calcd) = 5.092 g/cm³, F(000) = 1712, space group P2₁/n) and the structure of -Sb₃O₂F₅ is refined. The geometric characteristics of crystal structures of antimony(III) oxofluorides SbOF (L- and -forms) are compared with those of Sb₃O₂F₅ (- and -forms).