Crystalline Nitrate Research Articles

The effect of origin and physico-chemical properties on the kinetics of reduction of mixed NiO-Fe2O3 oxides with hydrogen

We investigated the effect of origin and some physico-chemical parameters on the kinetics of reduction with hydrogen of two series of mixed NiO-Fe2O3 oxides differing by their composition, the character of their precursors (mixed crystalline nitrates and coprecipitated hydroxides) and their decomposition temperature.This effect manifested itself by different magnitudes of specific surfaces of the mixed oxides and coherent regions of present phases as well as by different oxidizing abilities of the surface and differences in morphology and phase composition of corresponding samples in both series investigated. Nonlinear or nonmonotonous composition dependences of physico-chemical parameters investigated point to a mutual influence of individual components, which is also a function of the system origin and which modifies its reactivity during its reduction with hydrogen. The kinetics of the reduction was studied thermogravimetrically at 320-410 °C. The reduction of oxides of the hydroxide origin is catalytically accelerated by primarily reduced nickel, whereas in corresponding samples of the nitrate series, the total NiO is bound to the spinel phase and the reduction is delayed. Experimental IR spectra, the effect of preliminary annealing and DTA of the mixed oxides point to an inhibitory effect of water, which is constitutionally bound in trace admixtures of the goethite phase, on the kinetics of reduction of samples in the hydroxide series.

The kinetics of isothermal annealing of gamma-irradiation damage in crystalline barium nitrate

Abstract The annealing of γ-irradiation damage in crystalline barium nitrate at different temperatures in the range 370-430°C is a combination of a first-order process affecting a small portion of the fragments and a second-order process, with a higher energy of activation, governing the behaviour of the remainder ∼73%. The annealing data have been analysed on the models for simple interstitial vacancy recombination and also as a combination of a first-order and second-order process with an energy of activation of 10.9 and 24.0 kcal mole−1 respectively. It is considered that the first-order process is the combination of close-correlated pairs of O and NO2 fragments and the second order process involves the single reaction of random recombination of the fragments throughout the crystal.

Effect of temperature and phase state on the anharmocity of the vibrations of the nitrate ion in crystalline and molten nitrates

The effect of temperature--phase conversions on the vibrational spectra of nitrates has been studied in much detail [1-9]. Predominantly the temperature--phase changes of the parameters of the internal vibrations of the nitrate-ion (NO~) in the first-order spectral region have been studied. As for second-order spectra (SOS), these have been studied most fully only for Na, Rb, and Cs nitrates [3, 10-12]. Experimental study of the SOS permits the anharmonicity constants (AC) of the internal vibrations of the nitrate ion to be found. Knowledge of the AC of the nitrate ion and study of the effects of temperature and phase state on them enable a deeper understanding to be gained of the nature of the phase transitions in nitrates and of the associated changes in the interaction potentials of the atoms in NO7 during temperature-phase conversions.

The cyanobis(1,10-phenanthroline)platinum(II) complex in aqueous solution and as the crystalline nitrate. Nuclear magnetic resonance measurements and crystal-structure determination

The bis(1,10-phenanthroline)platinum(II) cation rapidly adds cyanide in aqueous solution forming the cyanobis-(1,10-phenanthroline)platinum(II) ion, which from 13C n.m.r. spectra has been shown to contain five-co-ordinated platinum both in water and in nitromethane solution. The crystals of cyanobis(1,10-phenanthroline)platinum(II) nitrate are triclinic, space group P, with Z= 2 and unit-cell dimensions a= 15.616(11), b= 7.264(6), c= 10.564(7)A, α= 102.81(4), β= 80.90(4), and γ= 96.47(4)°. The structure has been determined by the heavy-atom method from diffractometer data and refined to R= 0.031 for 3 562 independent reflections. Three nitrogen atoms from the phenanthroline groups and the carbon atom from the cyanide form an approximately square-planar configuration about the platinum; Pt–N(1) 2.062(5), Pt–N(2) 2.007(5), Pt–N(3) 2.053(5), and Pt–C(25) 1.931(6)A. The remaining nitrogen atom of the phenanthroline groups is at the apex of a square pyramid, Pt–N(4) 2.761 (5)A. In aqueous solution OH– and SH– appear to react analogously with the bis(1,10-phenanthroline)-platinum(II) ion. The cyano-complex is stable in solution and reacts only slowly with other nucleophiles (e.g. excess of CN–, OH–, and halide ions).

ChemInform Abstract: CONCERNING BAND ANALYSIS IN CRYSTALLINE NITRATES

AbstractDie bei niedrigen Frequenzen auftretende Asymmetrie bei der symmetrischen Valenzschwingung des Nitrations in den kristallinen Na‐, Ag‐ und Cs‐nitraten wird untersucht.

Concerning band analysis in crystalline nitrates

The origin of the low frequency asymmetry on the symmetrical stretching mode of the nitrate ion in crystalline nitrates of sodium, silver and caesium has been studied. The asymmetry has been shown to arise from a combination of correlation field splitting and the presence of ?hot? bands. Some factors influencing the position and intensity of the ?hot? bands are considered.

The enthalpy of formation of lead nitrate

The standard enthalpy of formation of crystalline lead nitrate has been determined by reaction calorimetry. A value: ΔHof {Pb(NO3)2, c} = − (105.32 ± 0.20) kcalth mol−1 was obtained.

Annealing of chemical radiation damage in crystalline barium nitrate

Results are reported on the isothermal annealing kinetics of gamma- irradiated Ba(NO/sub 3/)/sub 2/. Radiation doses were st run. Concent 50 Mrad, and the damage nitrite was estimated spectrophotometricaiiy. The annealing pattern is of an initial rapid reaction followed by a monotonically slow one. The fraction annealed is rather small, being st run. Concent 0.17 after 50 hr at 275 un. Concent 85% C. It is concluded that the diminution of the damage nitrite in Ba(NO/sub 3/)/sub 2/ is a true annealing phenomenon. (D.L.C.)

Absorption Spectra at 4°K of Single Crystals of Normal and Isotopically Substituted Sodium and Potassium Nitrates

Sharp line structure is observed in the low energy shoulder of the 3000-A absorption band of crystalline nitrates that have been cooled to 4°K. Single crystals of normal and of nitrogen-15 isotopically substituted sodium and potassium nitrates were examined spectrographically. Correlation between the spacings, polarization and orientation properties, isotope effect, and crystal field splitting of the spectra permitted their analysis. In terms of the D3h point symmetry of a free nitrate ion the excited electronic state is E′. This electronic configuration is one of three considered likely upon the basis of a LCAO molecular orbital treatment of the ion. The two asymmetric E′ vibrations of the ion predominantly contribute to the band structure. A large Franck-Condon shift, an extensive weakening of force constants, and the character of the excited vibrations indicate that the excited ion is planar but expanded with perhaps some, but not a great amount of asymmetric distortion. Predissociation appears at a level corresponding to a dissociation energy of 3.76 ev for the nitrate ion.

Raman spectra of some crystalline nitrates and sulphates

Raman spectra of some crystalline nitrates and sulphates

Raman Effect in Paramagnetic Crystals

VARIOUS crystalline sulphates have been examined for their Raman spectra by the same method as that used for crystalline nitrates and described previously (NATURE, Mar. 22, p. 463). The results indicate what appears to be a very remarkable influence of the paramagnetism of the cation on the intensities of the Raman lines. This appears very clearly when we compare the spectra of ferrous sulphate crystals (FeSO4, 7H2O) with those of other isomorphous sulphates, for example, magnesium or zinc. In the latter substances, a strong line appears with a frequency shift of about 980 cm.−1. This frequency is characteristic of the SO4−− ion, though its exact value shows considerable variations with the cation present in the crystal. In the spectrum of the ferrous sulphate crystals, however, the line fails to appear even when exposures are given of such duration that the feeble continuous spectrum accompanying the mercury lines comes out strongly on the plate. With aqueous solutions of ferrous sulphate, however, the SO4−− line appears feebly.

The magnetic anisotropy of crystalline nitrates and carbonates

Recent work in the field of magnetism emphasises the relation between the crystal structure and magnetic properties of solids. Such relations exist in all crystals whether ferromagnetic, paramagnetic or diamagnetic. We propose in this paper to discuss the explanation of the anisotropy of diamagnetic crystals, particularly some nitrates and carbonates with regard to which we have data from the measurements of Voigt and Kinoshita and very recently of Rabi. These substances are especially simple because, as is well-known from the work of Kossel, Bragg and others, they consist of charged ions held together by electrostatic forces, so that we can attribute the magnetic anisotropy of the crystal to that of the individual ions. Thus, for instance, in the case of sodium and potassium nitrates we may reasonably look for the explanation of observed magnetic anisotropy of the crystal in the structure of the nitrate ion, since presumably the metallic ions are more or less isotropic. It is significant in this connection that nitric acid solution has been found by Cotton and Mouton to exhibit a measurable magnetic birefringence, thus indicating that the NO 3 - ion has a pronounced magnetic anisotropy even in the liquid state. It is possible to estimate this anisotropy in a purely optical way by combining the data for magnetic double-refraction with the measurements of the depolarisation of the light scattered in nitric acid. It is found that the magnetic anisotropy of the NO 3 group thus found, practically agrees with that necessary, as remarked above, to explain the magnetic properties of the crystalline nitrates.

The Birefringence of Crystalline Carbonates, Nitrates and Sulphates

IN two very interesting papers (Proc. Roy. Soc., vol. 105, p. 370, and vol. 106, p. 346, 1924) Prof. W. L. Bragg put forward an explanation of the strong birefringence exhibited by the crystalline carbonates and nitrates. Expressed very briefly, his theory is that in the carbonate and nitrate ions the oxygen atoms are situated in one plane around the central carbon or nitrogen atom, as the case may be, and that, as the result of this arrangement and of the mutual influence of the electric doublets induced in the atoms by the field of the light-waves, the refractivity of the group depends to a marked extent on the direction of the light-vector. The refractive indices of the crystal were successfully computed on this basis. The crystalline sulphates are known, on the other hand, to have a very weak birefringence, and the suggestion was made that very probably the oxygen atoms are arranged tetrahedrally round the sulphur atom in the sulphate ion group, thus making it optically isotropic.