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[en] The literature data on equilibrium with the participation of cobalt fluorides and their negative ions are analyzed. Enthalpies of formation −∆fH°(0 K) are determined (kJ/mol): CoF3, 568.9 ± 8; , 972.4 ± 10; CoF4, 639.4 ± 12; , 1228.0 ± 17.
[en] This article considers obtaining and thermodynamic characteristics of cobalt (II) and nickel (II) fluorides. Therefore, tetrahydrate of cobalt (II) and nickel (II) fluorides have been obtained by interaction of corresponding metal of hydroxo carbonate with hydrofluoric acid solutions of different concentrations. The enthalpy value of this and adverse reactions has been determined by means of calorimetry method. According to thermochemical cycle, the values of enthalpy of formation of tetrahydrate fluorides and hydroxo carbonates of cobalt (II) and nickel (II) have been defined. (author)
[en] ZnF3-CoF2 systems (Ln - Gd, Tb, Dy, Ho, Er, Tm) have been studied by differential thermal-, crystallooptical and X-ray phase analyses methods. State diagrams of these systems are built. LnF3-CoF2 systems (Ln - Tb, Dy, Ho) are shown to be simple eutectic ones with boundary solid solutions on the base of cobalt difluoride. LnF3-CoF (Ln - Gd, Er, Tm) systems are of eutectic type with nonvariant metatectic equilibrium between a liquid phase and high-temperature modification of REE trifluoride
[en] Taking into account the inexhaustible interest in studying the peculiarities of physical properties in the neighborhood of phase transitions and the growth of experimental investigations of cobalt fluoride, we have studied the peculiarities of magnetic susceptibility in the vicinity of the critical field HC at which cobalt fluoride performs the second-order phase transition from the antiferromagnetic phase to the angular phase. It is discovered that in the magnetic field H ‖ C4, the magnetic susceptibility becomes infinite at H → HC. It is shown that as the magnetic field direction deviates from the C4 axis, the magnetic susceptibility in the critical field HC proves to be finite. It is also shown that the change in the magnetic susceptibility with the change in the magnetic field considerably decreases at extremely insignificant deviations of the field H from the C4 axis. Since the calculations are performed in terms of the Landau theory of phase transitions, we pay attention to the similarity and difference between the obtained results and those in the vicinity of the Curie point obtained by using the Landau theory of phase transitions.
[en] In this theoretical and experimental study, the ability of carbonyl fluoride (COF_2) and carbonyl chloride fluoride (COFCl) to form noncovalent interactions with the Lewis base dimethyl ether (DME) is assessed. From ab initio calculations, two stable complexes are found for COF_2·DME, both formed through a lone pair⋯π interaction. FTIR measurements on liquefied noble gas solutions, supported by ab initio calculations, statistical thermodynamical calculations and Monte Carle Free Energy Perturbation calculations, show that a 1:1 lone pair⋯π bonded complex is found in solution, with an experimental complexation enthalpy of −14.5(3) kJ mol"−"1. For COFCl·DME three lone pair⋯π complexes, as well as a Cl⋯O halogen bonded complex, are found from ab initio calculations. Experimentally, clear complex bands for 1:1 lone pair⋯π complexes are observed, with an experimental complexation enthalpy of −11.4(2) kJ mol"−"1. Furthermore, indications of the presence of a small amount of the halogen bonded complex are also observed.
[en] Cobalt metal of exceptional purity is needed for distinguished applications in the hard metal and nuclear industries. It is well recognized as a binder in the cemented carbide tools. The uses of equal merit in the nuclear field are (a) 60Co, a gamma active source, (b) self powered neutron detector and (c) control material due to high 0. India is devoid of primary resources of cobalt. A small tonnage of cobalt produced in the private sector from imported cobalt concentration/ intermediate do not qualify to meet the above uses. As a result such requirements are presently being met by imports. This paper presents, an account of the developmental work conducted to recover cobalt values in the form of Co compounds from indigenously available secondary resources, followed by conversion of cobalt compounds to metal of exceptional purity and submicron size by two different novel techniques