Vibrational spectroscopy of selected minerals of the rosasite group

Minerals in the rosasite group namely rosasite, glaucosphaerite, kolwezite, mcguinnessite have been studied by a combination of infrared and Raman spectroscopy. The spectral patterns for the minerals rosasite, glaucosphaerite, kolwezite and mcguinnessite are similar to that of malachite implying the molecular structure is similar to malachite. A comparison is made with the spectrum of malachite. The rosasite mineral group is characterised by two OH stretching vibrations at approximately 3401 and 3311 cm-1. Two intense bands observed at approximately 1096 and 1046 cm-1 are assigned to nu1(CO3)2- symmetric stretching vibration and the delta OH deformation mode. Multiple bands are found in the 800-900 and 650-750 cm-1 regions attributed to the nu2 and nu4 bending modes confirming the symmetry reduction of the carbonate anion in the rosasite mineral group as C2v or Cs. A band at approximately 560 cm-1 is assigned to a CuO stretching mode.     

Mathematics in Colleges of Education

A brief review is given of the main developments that have taken place in colleges of education in the past ten years. Against this background there follows a discussion of the work of a mathematics department within a college and some of the problems of providing viable courses for both future specialist teachers and for future teachers in primary schools. Student attitudes and abilities, objectives of courses, methods of teaching and assessment are considered. In conclusion some possible ways are suggested of ameliorating a situation which is not altogether satisfactory.     

Thermal decomposition and X-ray diffraction of sulphate efflorescent minerals from El Jaroso Ravine, Sierra Almagrera, Spain

Two evaporite minerals from the El Jaroso Ravine, Spain have been analysed by thermogravimetry coupled with an evolved gas mass spectrometer. X-ray diffraction results proved the evaporite minerals were a mixture of sulphates including the minerals magnesiocopiapite, coquimbite and possibly alunogen. Thermal decomposition of the unoxidised samples showed steps at 52, 99 and 143 °C confirmed by mass spectrometric results and attributed to adsorbed water, interstitial water and chemically bonded water. This evaporite mineral rock showed two higher temperature decomposition steps at 555 and 599 °C with mass losses of 19.6 and 7.8%. Slightly different temperatures for the thermal decomposition of the oxadada sample were observed at 52, 64.5 and 100 °C. Two higher temperature mass loss steps at 560.5 and 651 °C were observed for the oxidised sample. By comparison of the thermal analysis patterns of halotrichite and jarosite it can be shown that the El Jaroso samples are mineral sulphates and not halotrichite or jarosite.     

Infrared and infrared emission spectroscopy of the zinc carbonate mineral smithsonite

Infrared emission and infrared spectroscopy has been used to study a series of selected natural smithsonites from different origins. An intense broad infrared band at 1440cm(-1) is assigned to the nu(3) CO(3)(2-) antisymmetric stretching vibration. An additional band is resolved at 1335cm(-1). An intense sharp Raman band at 1092cm(-1) is assigned to the CO(3)(2-) symmetric stretching vibration. Infrared emission spectra show a broad antisymmetric band at 1442cm(-1) shifting to lower wavenumbers with thermal treatment. A band observed at 870cm(-1) with a band of lesser intensity at 842cm(-1) shifts to higher wavenumbers upon thermal treatment and is observed at 865cm(-1) at 400 degrees C and is assigned to the CO(3)(2-)nu(2) mode. No nu(2) bending modes are observed in the Raman spectra for smithsonite. The band at 746cm(-1) shifts to 743cm(-1) at 400 degrees C and is attributed to the CO(3)(2-)nu(4) in phase bending modes. Two infrared bands at 744 and around 729cm(-1) are assigned to the nu(4) in phase bending mode. Multiple bands may be attributed to the structural distortion ZnO(6) octahedron. This structural distortion is brought about by the substitution of Zn by some other cation. A number of bands at 2499, 2597, 2858, 2954 and 2991cm(-1) in both the IE and infrared spectra are attributed to combination bands.     

Electrochemical Studies of Vitamin K1 Microdroplets: Electrocatalytic Hydrogen Evolution

The voltammetry of a basal-plane pyrolytic graphite electrode modified with a random ensemble of unsupported microdroplets of vitamin K₁ is investigated when the electrode is immersed in aqueous electrolytes. It is shown that in dilute acidic solutions, electroreduction occurs in a single two-electron two-proton process to yield the corresponding hydroquinone at the electrode|vitamin K₁ microdroplet|aqueous-electrolyte three-phase boundary. On addition of ionic alkali-metal salts to the aqueous acidic phase, the electrochemical reduction of vitamin K₁ to the quinol is accompanied by catalytic hydrogen evolution within and alkali-metal-cation insertion into the organic microdroplets. In strongly alkaline solutions, electrochemical reduction of vitamin K₁ at the triple-phase junction is proposed as being a single two-electron process with concomitant uptake of alkali-metal cations in order to maintain electroneutrality within the oil phase. Surprisingly, the relative ease of cation insertion into the oil phase is demonstrated to be governed by the degree of ion-pair formation rather than by the Gibbs transfer energy of the cation across the liquid|liquid interface.     

Identification of the rosasite group minerals--an application of near infrared spectroscopy

The ability of near infrared reflectance spectroscopy to classify the rosasite group minerals from spectral characteristics is demonstrated. NIR spectroscopy can be regarded as an alternative tool for structure analysis. The spectra show that rosasite group minerals with different cations can be distinguished. Ni2+ in nullaginite [Ni2(CO3)(OH)2] is conspicuous through a single broad band absorption feature at 8525 cm-1, extended from 11,000 to 7000 cm-1. The effect of Ni on Cu is seen in the spectrum of glaukosphaerite [(Cu, Ni)2(CO3)(OH)2] both by a red shift of the spectrum and reduction in intensity of bands with variable positions of band maxima for Cu2+ at 6995 cm-1 and Ni2+ at 7865 cm-1. The spectrum of rosasite [(Cu, Zn)2(CO)3(OH)2] is characterised by Cu2+ band at 7535 cm-1. Kolwezite [(Cu, Co)2(CO)3(OH)2] is a spectral mixture of Cu and Co but optically separated by Co2+ and Cu2+ peaks at 8385 and 7520 cm-1. Vibrational spectra of carbonates show a number of bands in the 7000-4000 cm-1 region attributable to overtones, combination of OH stretching and deformation modes. They appear to be uniform in nature since the structure of rosasite group minerals is identical. The complexity of these features varies between samples because of the variation in composition and hence is useful for discriminating different hydrous carbonates.