The structure of the mineral leogangite Cu10(OH)6(SO4)(AsO4)4·8H2O--implications for arsenic accumulation and removal

The vibration characterization of synthetic crystalline lead hydrogen arsenite chloride precipitates Pb2(HAsO3)Cl2-implications of solidification of As (III) and Pb (II)

The lead hydrogen arsenite chloride precipitates (Pb2(HAsO3)Cl2) are synthesized hydrothermally due to its structure trap for lead and arsenic. The synthetic precipitates have well-developed crystalline. The crystals of lead hydrogen arsenite chloride have a series of obvious IR bands at 790, 721, 645, 589 and 554 cm(-1). These bands are assigned to the Ag mode of As-O stretching vibration (790), the antisymmetric stretch of As-OH (721), Ag modes (554 and 589) and E1g (645) of the symmetric deformation (ν1 and ν3) of AsO3 unit. The Raman bands at 782, 723, 586, 559 cm(-1) are attributed to As-O stretching vibration (ν1) and the symmetric deformation (ν1 and ν3), of which the positions and assignments display in accordance with IR result. The most intense Raman band is found in 814 cm(-1) and is attributed to the Ag mode of ν1 symmetric stretching vibration of AsO3 unit, which is not active in IR. The SEM image shows that the precipitates have needle morphology.

A spectroscopic study of Brazilwood paints in medieval books of hours

In this work, microspectrofluorimetry was for the first time applied to the identification of the red organic lakes that are characteristic of the lavish illuminations found in 15(th) century books of hours. Microspectrofluorimetry identified those red paints, ranging from opaque pink to dark red glazes, as brazilwood lakes. An unequivocal characterization was achieved by comparison with reference paints produced following recipes from the medieval treatise The Book on How to Make Colours, and was further confirmed by fiber optic reflectance spectroscopy (FORS). For these treasured cultural objects, microspectrofluorimetry and FORS proved to be the only techniques that could identify, in situ or in microsamples, the chromophore responsible for the pinkish hues: a brazilein-Al(3+) complex. Additionally, a multi-analytical approach provided a full characterization of the color paints, including pigments, additives, and binders. Microspectroscopic techniques, based on infrared and X-ray radiation, enabled us to disclose the full palette of these medieval manuscripts, including the elusive greens, for which, besides malachite, basic copper sulfates were found; Raman microscopy suggested a mixture of brochantite and langite. Infrared analysis proved invaluable for a full characterization of the additives that were applied as fillers or whites (chalk, gypsum, and white lead) as well as the proteinaceous and polysaccharide binders that were found pure or in mixture.

Whelanite Ca₅Cu₂(OH)₂CO₃,Si₆O₁₇·4H₂O--a vibrational spectroscopic study

Whelanite Ca(5)Cu(2)(OH)(2)CO(3),Si(6)O(17)·4H(2)O is a hydrated hydroxy mixed anion compound with both silicate and carbonate anions in the formula. The structural characterisation of the mineral whelanite remains incomplete. Whelanite is probably a neosilicate with Cu(2+) in square planar coordination. Two Raman bands at 1070 and 1094 cm(-1) are assigned to the ν(1) symmetric stretching modes of the CO(3)(2-) units. The observation of two symmetric stretching modes supports the concept of two non-equivalent CO(3)(2-) units in the whelanite structure. The intense sharp Raman band at 1006 cm(-1) is assigned to the ν(1) (A(1g)) symmetric stretching vibration of the Si(6)O(17) units. The splitting of the ν(3) vibrational mode offers support to the concept that the SiO(4) tetrahedron in whelanite is strongly distorted. A very intense Raman band observed at 666 cm(-1) with a shoulder at 697 cm(-1) is assigned to the ν(4) vibrational modes. Intense Raman bands at 3534, 3556, 3550 and 3595 cm(-1) are assigned to the stretching vibrations of the OH units. Low intensity Raman bands at 2910, 3187 and 3453 cm(-1) are assigned to water stretching modes. Thus, vibrational spectroscopy has been used to characterise the molecular structure of whelanite. Whelanite is a mineral that could be conceived as a healing mineral.

A vibrational spectroscopic study of planchéite Cu₈Si₈O₂₂(OH)₄·H₂O

Planchéite Cu(8)Si(8)O(22)(OH)(4)·H(2)O is a hydrated copper hydroxy silicate. Raman spectroscopy complimented with infrared spectroscopy has been used to determine the molecular structure of planchéite. Raman bands at around 1048, 1081 and 1127 are described as the ν(1)-SiO(3) symmetric stretching vibrations; Raman bands at 828, 906 are attributed to the ν(3)-SiO(3) antisymmetric stretching vibrations. The Raman band at 699 cm(-1) is assigned to the ν(4) bending modes of the -SiO(3) units. The intense Raman band at 3479 cm(-1) is ascribed to the stretching vibration of the OH units. The Raman band at 3250 cm(-1) is evidence for water in the structure.

Raman spectroscopy of the multi-anion mineral schlossmacherite (H3O,Ca)Al3(AsO4,PO4,SO4)2(OH)6

The mineral schlossmacherite (H(3)O,Ca)Al(3)(AsO(4),PO(4),SO(4))(2)(OH)(6), a multi-cation-multi-anion mineral of the beudantite mineral subgroup has been characterised by Raman spectroscopy. The mineral and related minerals functions as a heavy metal collector and is often amorphous or poorly crystalline, such that XRD identification is difficult. The Raman spectra are dominated by an intense band at 864cm(-1), assigned to the symmetric stretching mode of the AsO(4)(3-) anion. Raman bands at 809 and 819cm(-1) are assigned to the antisymmetric stretching mode of AsO(4)(3-). The sulphate anion is characterised by bands at 1000cm(-1) (ν(1)), and at 1031, 1082 and 1139cm(-1) (ν(3)). Two sets of bands in the OH stretching region are observed: firstly between 2800 and 3000cm(-1) with bands observed at 2850, 2868, 2918cm(-1) and secondly between 3300 and 3600 with bands observed at 3363, 3382, 3410, 3449 and 3537cm(-1). These bands enabled the calculation of hydrogen bond distances and show a wide range of H-bond distances.