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The structures of four crystalline phases of fananserine have been solved and their melting properties determined. The p-T diagram for this tetramorphism has been constructed by combining these data. Three out of the four solids are associated with stable p-Tdomains. Two of them have a low-pressure enantiotropic character in narrow p-T domains. The fourth one is intrinsically metastable. The stability ranking agrees with that inferred from solubility measurements at room temperature.

Racemic Zopiclone crystallises as a dihydrate (DH) or as a conglomerate (A). Upon heating, DH dehydrates to an anhydrous racemate (B) which transforms into the 1:l mixture of enantiomers (A). It can be inferred from crystallographic and thermodynamic data that the anhydrous racemate is metastable with respect to the 1:l mixture of enantiomers (A) whatever the water vapour pressure and the temperature. Thus, the B → A transition appears to occur monotropically.

ZnxTiyOzlayers were prepared by sol–gel method and nitridated yielding photoactivity in the visible wavelength region. The condensation process of these nanostructures and their subsequent sintering was followed by using XRD-, UV/Vis-, micro-Raman-, FTIR- and thermal analysis measurements. The oxynitride formation during the nitridation process was confirmed by XPS and UV-Vis spectroscopy. The photocatalytical studies of methylene blue (MB) degradation revealed the activity of coloured oxynitride layers under the visible light irradiation. Furthermore, a metachromasy of MB infiltrated within the nanostructured films was observed for the first time. This blue shift in the optical absorption spectrum of MB became even more pronounced during the photodegradation process of this dye.

A previously published four-parameter empirical equation of state of liquids is modified twice in order to improve the p, V, T data representation and its physical meaning, respectively. The first modification, a six-parameter relationship with two pressure square-root terms, was applied to 57 liquid compounds and to 6 mixtures and gives a very good representation (average percentage deviations of specific volume values less than 0.3%) of p, V, T data encompassing large pressure domains (0.1 to 1200 MPa). It could be useful for engineering applications. The second modified relationship exhibits the same fitting characteristics as the four-parameter one, but it has a better physical meaning. This equation contains an adjustable positive coefficient ξ which accounts for the intersections of the (∂α/∂p)T isotherms at high pressure and also for the variations of the “ pressure coefficient ” (∂p/∂T)V as a function of both volume and temperature. Thermal expansion data may be represented with an average percentage deviation better than 5%.

Crystals of a C60 1:1 solvate (I-centered cubic, a = 23.284(2) Å) were grown by evaporating solutions of C60 in H2CCl2 at room temperature. Solvate crystals are not air stable and spontaneously transform into a hexagonal polymorph of C60 (a = 10.044(5) Å, c = 16.404(8) Å, c/a = 1.633(2)) when extracted from the mother liquor at room temperature. Although solvate formation entails almost no volume change, desolvation enthalpy (59.2 kJ/mol of solvent) is found to be about twice as high as sublimation enthalpy for pure H2CCl2.

Single and 10-fold-twinned crystals of the C60 1:1 solvate formed with 1,1,2-trichloroethane were examined by means of scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry and thermogravimetry. Solubility of C60 in 1,1,2-trichloroethane was found to be 130 ± 10 mg per liter of solution in equilibrium with solvate crystals at 296 ± 2 K. The lattice metrics of the solvate is orthorhombic (a = 10.164(3) Å, b = 31.390(6) Å, c = 10.130(4) Å, β = 90.00(2)°), with axis c as a twin axis, although the symmetry is monoclinic (space group P21/n). The solvate forms with a negative excess volume (−58 ų per formula unit), and its packing coefficient (0.76) is higher than that for close packing of hard spheres. On heating, desolvation into cubic C60 and TCAN vapor occurs in one step at 436 K (onset) with a related enthalpy, +48 kJ per mole of solvate, close to the sublimation enthalpy for pure solvent. On aging at room temperature in the dark, no degradation of big (≈1 × 10−³ mm³) solvate crystals into fcc C60 is observed after 4 years have elapsed.

Measurements of the masses of incorporated water and of the heats of hydration have been performed at 310 K, under air atmosphere saturated with water vapour, on three differently dehydrated samples of the Saccharomyces boulardii yeast in order to evaluate differences in physicochemical properties related to the following dehydration processes: cryodesiccation (or lyophilization) and thermodesiccation (spray drying and in-fluidized-bed heating).

A new phenomenon has been unexpectedly discovered in studying transitions between crystal phases A, B, and C of n-alkanoic acids mixed with ordinary glass powder. Post-melting and pre-freezing events have been observed on scanning temperature at atmospheric pressure by means of a DSC calorimeter and on scanning pressure isothermally using a piezothermal apparatus. These phenomena have been interpreted as the melting and freezing of an assembly of Langmuir−Blodgett-like films of alkanoic acids adsorbed on the glass surface. Freezings and meltings could be observed at temperatures 10 to 15 °C higher than the conventional melting point or at pressures as much as 500 bar lower than the expected melting pressures. Optical microscopy allowed the phenomenon to be observed. The glass mixtures with lignoceric acid were thoroughly investigated at two different mass fractions. At atmospheric pressure, independent of the acid content, deposition of acid on the glass surface was achieved only at the end of a slow process of adsorption requiring repeated melting and freezing cycles. In the case of a mixture containing a poor quantity of acid, the adsorption process could be controlled by the gradual diminution and disappearance of the melting and freezing peaks of the bulk acid. On the contrary, the adsorption was completed from the first rise of pressure in the case of the piezothermal scans. In addition, both scan types showed the occurrence of new transitions after the completion of surface melting. They have been attributed to the transformation of the surface crystal into liquid-crystal-like structures onto the glass surface. In piezothermal scans, the pressure range within which transitions occurred became wider with increasing temperature.

The nootropic drug Piracetam is known to crystallize in three phases. In order to obtain their stability hierarchy from sublimation pressure inequalities, the drawing of a topologicalp,Tdiagram was attempted. For such a purpose and also for quality control, crystallographic and thermodynamic data were required. Powder X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) were used. Molecular energy calculations were performed. Phase I melts at 426K (ΔfusH(I) = +180 J·g−1). Phase II transforms into Phase I at 399K (Δ(II→I)H= +24 J·g−1). Phase III transforms into phase I at 392K (Δ(III→I)H= +28 J·g−1) or melts at 412K (ΔfusH(III) = +210 J·g−1). Thep,Tdiagram shows that phase I is stable at higher temperature and phase II at lower temperature, like phase III, which is stable under high pressure. At room temperature, phase II is the more stable form, and phase I the less stable one. This agrees with the spontaneous I → II transformation observed at 298K within a few hours, and with lattice energies, calculated previously. Molecular energy calculations and crystal structure comparison show how intermolecular hydrogen bonds and H-bonded dimers, in phases II and III, may stabilize conformations higher in energy than those of the isolated molecule and of phase I.

Prismatic crystals of orthorhombic 1:1 solvate (space group Pnma or Pn21a, α = 31.47 Å, β = 10.07 Å, c = 10.22 Å, Z = 4) are obtained by slowly evaporating trichlorethylene solutions of C60 at room temperature. Decagonal morphologies, i.e. crystals with angles of about 36° between adjacent faces, are also encountered. Although the enthalpy of desolvation, + 51.3 J per gram of solvate (+ 43.7 kJ per mole of solvent), is close to that of sublimation for pure solvent (+ 40.6 kJ mo1-1), the formation of the solvate from its solid components is accompanied with a negative excess volume (-40 Å3 per formula unit).

By slowly evaporating at room temperature solutions of C60 in n-octane, crystals of the hexagonal solvate C60 1 n-octane have been obtained (a = 10.10, c = 10.18 Å)., Although these crystals are formed with a negative volume excess of - 24 Å3 per formula-unit, their desolvation enthalpy, 60 J g-1 (50 kJ mol-1), is close to the sublimation enthalpy of pure n-octane.