High resolution conductometry for isotopic assay of deuterium in mixtures of heavy water and light water

A PC based high resolution conductivity monitoring technique has been deployed for determination of isotopic purity of heavy water in samples containing heavy water and light water mixtures using pulsating sensor based conductivity monitoring instrument. The technique involves accurate determination of conductivities of a series of specially treated heavy water and light water mixtures of various compositions at a constant solution temperature. The shift in conductivity (Δκ), which is the difference between conductivities of composite mixture after and before the formation of a typical complex compound (boric acid–mannitol complex in this case), shows a smooth and reproducible decreasing trend with increase in percentage composition of heavy water. This relation, which is obtained by appropriate calibration, is used in the software program for direct display of isotopic purity of heavy water. The technique is examined for determination of percentage composition of heavy water in the entire range of concentration (0–100 %) with reasonable precision (relative standard deviation, RSD ≤1.5 %). About 1 mL of sample is required for each analysis and analysis is completed within a couple of minutes after pretreatment of sample. The accuracy in measurement is ≤1.75 %.     

MAS-NMR investigations of the crystallization behaviour of lithium aluminum silicate (LAS) glasses containing P2O5 and TiO2 nucleants

Lithium aluminum silicate (LAS) glass of composition (mol%) 20.4Li₂O-4.0Al₂O₃-68.6SiO₂-3.0K₂O-2.6B₂O₃-0.5P₂O₅-0.9TiO₂ was prepared by melt quenching. The glass was then nucleated and crystallized based on differential thermal analysis (DTA) data and was characterized by ²⁹Si, ³¹P, ¹¹B and ²⁷Al MAS-NMR. XRD and ²⁹Si NMR showed that lithium metasilicate (Li₂SiO₃) is the first phase to c form followed by cristobalite (SiO₂) and lithium disilicate (Li₂Si₂O₅). ²⁹Si MAS-NMR revealed a change in the network structure already for the glasses nucleated at 550 °C. Since crystalline Li₃PO₄, as observed by ³¹P MAS-NMR, forms concurrently with the silicate phases, we conclude that crystalline Li₃PO₄ does not act as a nucleating agent for lithium silicate phases. Moreover, ³¹P NMR indicates the formation of M-PO₄ (M=B, Al or Ti) complexes. The presence of BO₃ and BO₄ structural units in all the glass/glass-ceramic samples is revealed through ¹¹B MAS-NMR. B remains in the residual glass and the crystallization of silicate phases causes a reduction in the number of alkali ions available for charge compensation. As a result, the number of trigonally coordinated B (BO₃) increases at the expense of tetrahedrally coordinated B (BO₄). The ²⁷Al MAS-NMR spectra indicate the presence of tetrahedrally coordinated Al species, which are only slightly perturbed by the crystallization.     

Polarisation studies on the Raman spectra of cubic crystals

General expressions have been derived for the intensities of the three classes of Raman lines namely totally symmetricA, doubly degenerateE and triply degenerateF, in the case of cubic crystals under the following conditions. The direction of the incident beam which is polarised with its electric vector inclined at an angleα to the normal to the scattering plane makes an angleΘ with one of the cubic axes of the crystal. The transversely scattered light is analysed by a double image prism with its principal axes inclined at angleβ to the normal to the scattering plane, which is horizontal. For incident unpolarised light and Θ=22 1/2°, and the scattered light being analysed by a double image prism rotated through 45° from the position when its principal axes are vertical and horizontal? forA lines is equal to one, forE lines >1 and forF lines <1. This gives a method of classifying the Raman lines of a cubic crystal in a single setting. The results have been experimentally verified in sodium chlorate.     

Synthesis of Some Spirooxazolidinones

In this communication, we wish to report the synthesis of some new spiro-4-oxazolidinones. Treatment of the potassium salt of 2-methyl-cyclohexane-1,3-dione (1) with α-chloroacetanilides (2 a-c) gave 4-aryl-6-methyl-1-oxa-4-aza-spiro [4,5] deca-3,7-diones (3 a-c); and with α-halopropionanilides (2 d,e), the corresponding 4-aryl-2,6-dimethyl-1-oxa-4-aza-spiro [4,5] deca-3,7-diones (3 d, e) were obtained.     

Some studies on the phase formation and kinetics in TiO<Subscript>2</Subscript> containing lithium aluminum silicate glasses nucleated by P<Subscript>2</Subscript>O<Subscript>5</Subscript>

Lithium aluminum silicate (LAS) glasses of compositions (wt%) 10.6Li₂O–71.7SiO₂–7.1Al₂O₃–4.9K₂O–3.2B₂O₃–1.25P₂O₅–1.25TiO₂ were prepared by the melt quench technique. Crystallization kinetics was investigated by the method of Kissinger and Augis–Bennett using differential thermal analysis (DTA). Based on the DTA data, glass ceramics were prepared by single-, two-, and three-step heat treatment schedules. The interdependence of different phases formed, microstructure, thermal expansion coefficient (TEC) and microhardness (MH) was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-mechanical analysis (TMA), and microhardness (MH) measurements. Crystallization kinetics revealed that Li₂SiO₃ is the kinetically favored phase with activation energy of 91.10 kJ/mol. An Avrami exponent of n = 3.33 indicated the dominance of bulk crystallization. Based upon the formation of phases, it was observed that the two-stage heat treatment results in highest TEC glass ceramics. The single-step heat treatment yielded glass ceramics with the highest MH.     

Raman spectra of crystalline double sulphates Part II. Ammonium double sulphates

Raman spectra of single crystals of (NH₄)₂M(SO₄)₂·6 H₂O whereM=Mg, Zn Ni or Co have been recorded using λ 2537 excitation. Interesting results concerning the substitution of the divalent atoms in the double sulphate lattice on the sulphate and ammonium frequencies are observed. The spectra of these double sulphates are discussed in the light of the known crystal structure details and in relation, to the spectra of the corresponding potassium double sulphates, reported recently by the author. The Raman spectrum of NaNH₄SO₄·2 H₂O has also been recorded for the first time and the results obtained are also included.