A. Rafalska-Lasocha

X-ray powder diffraction investigation of green earth pigments

Laboratory X-ray powder diffraction was used to investigate mineralogical compositions of green pigments labeled by suppliers as “green earths.” It was found that glauconite and celadonite—minerals historically considered as the main ingredient of this pigment—were present only in Bohemian green earth, green earth from Thuringen (glauconite), and Bavarian green earth (celadonite). Other investigated pigments consist of mineralogical-component minerals with added synthetic organic colorants. The obtained results may be useful for scientists, restorers, and artists in proper choices of the pigments they use in their works.

X-ray powder diffraction structural studies of lithol red pigments

Lithol reds belong to the group of azo pigments which were popular artists’ pigments at the beginning of the twentieth century. Under the name lithol red pigment, one can find a family of sodium (PR 49), barium (PR 49:1), calcium (PR 49:2), and strontium (PR 49:3) salts of diazotised Tobias (2-naphthylamine-1-sulphonic) acid coupled with 2-naphthol. The colour of the pigment ranges from yellowish red (sodium salt) to bluish red (strontium salt), depending on the metal cation. The main drawback of lithol red is its very poor lightfastness, which has profound implications for its artistic use (e.g. Mark Rothko’s Seagram and Harvard Murals) [1].

On the grounds of icons from National Museum in Krakow

Among various types of cultural heritage objects, icons belong to the most interesting and not too often investigated group. Similarly to the investigations of easel paintings, only tiny amounts of samples taken from icons can be available for scientific studies. In the literature very few technical papers on icons can be found, so there is a shortage of information for comparative studies in this subject.

Octamolybdates – promising materials for industry and medicine

desirable to attach organic functionalities covalently to the surface of polyoxoanions. As part of a broad program centered on the functionalization of polyoxometalates, we have been interested in the derivatisation of Lindqvist type polyoxoanions with organosilyl moieties. The condensed polyoxometalate (nBu4N)4[(TaW5O18)2O] which is synthesized by reacting [TaW5O19] with BuSnCl3, crystallises in the orthorhombic system, space group Pbnb with lattice parameters a = 15.7981(14), b = 17.939(3), c = 35.216(6)Å, V= 9980 Å and Z = 4. The crystallographic study of(nBu4N)4[(TaW5O18)2O] shows that the dimer is composed from two polyoxoanions fragments linked by linear Ta-O-Ta bridge. Such a linkage readily reacts with organosilyl (Lewis electrophilic reagents), such as RR’ 2SiOH (R = R’ = Et, iPr, OtBu, Ph; R = tBu, R’ = Me) to yield monomeric plenary Lindqvist derivatives (nBu4N)2[W5O18Ta(O)SiR’R2]. These derivatives are characterized in the solid state by IR and in solution by multinuclear NMR (C, Si, W). The crystallographic study of (nBu4N)2[(W5O18Ta(O)SiPh3)]indicates that {SiPh3} is grafted on the surface of the polyanion through the terminal Ot-Ta oxygen atom.

X-ray powder diffraction investigations of phenol derivatives

The X-ray powder diffraction patterns of three phenol derivatives—2-chlorophenol, 2,6-dichloro-4-nitrophenol, and 2,6-dichloro-phenoloindophenol tetrahydrate—were collected and the lattice parameters of these compounds were determined. The measurement for 2-chlorophenol was carried out at 250 K in a low-temperature chamber; this compound crystallizes in hexagonal system with a=1.59602(8) nm, c=0.59761(7) nm, space group P6 or P6 3 /m. Investigated at room temperature, 2,6-dichloro-4-nitrophenol and 2,6-dichloro-phenoloindophenol tetrahydrate crystallize in the triclinic system with the unit cell parameters refined to a=0.8169(2) nm, b=1.6637(6) nm, c=0.7440(1) nm, α=96.6(3)°, β=116.19(2)°, γ=78.68°, and space group P-1(2), and a=0.7792(3) nm, b=1.2795(4) nm, c=0.7256(3) nm, α=91.17(5)°, β=96.93(4)°, γ=85.41(3)°, and space group P-1(2), respectively.