T. Calvet

Application of the “shape-factors method” to purity analysis of compounds by thermal methods

Abstract The shape-factors method may be applied to the determination of phase diagrams by thermal methods. In this paper, its applicability to purity evaluation of compounds (organic and inorganic) is discussed. It is a rapid and easy method which can be applied either to impurities which form a eutectic phase diagram with the main component or to impurities miscible in the solid state with the compound to be purified.

Molecular alloys in the series of para disubstituted benzene derivatives: Part III. The para-bromochlorobenzene-para-dibromobenzene system

Abstract This paper discusses the binary system between para-bromochlorobenzene and para-dibromobenzene. The phase diagram and crystalline parameters of the molecular alloys of this system have been determined by DSC and X-ray diffraction. The miscibility versus temperature study has shown a miscibility in all proportions in the solid state between room temperature and the melting points. The evolution of the alloy crystalline parameters with the composition shows that the deformation of the para-bromochlorobenzene (pBCB) by introducing para-dibromobenzene (pDBB) takes place mainly in the a direction.

Crystal structure determination of 1-pentanol from low-temperature powder diffraction data by Patterson search methods

In the course of our research on normal alkanols, the crystal structure of 1-pentanol has been solved by applying Patterson-search methods to laboratory powder X-ray diffraction data recorded on a curved position-sensitive detector (CPS120) at 183 K. The crystal structure was refined with the rigid-body Rietveld least-squares method. The cell is monoclinic, space group P 2 1 ∕ c , Z =4, and the cell parameters are a =15.592(9) A, b =4.349(1) A, c =9.157(1) A, β =104.7(7)°, V =600.6(3) A 3 . There is one molecule in the asymmetric unit with the O–H bond in gauche conformation with respect to the alkyl skeleton. Packing is defined by the hydrogen bonds linking the 1-pentanol molecules along zigzag chains parallel to b .

Molecular alloys in the series of paradisubstituted benzene derivatives. IV. Parabromochlorobenzene-parachloroiodobenzene system

Abstract The stability of mixed crystals between parabromochlorobenzene (pBCB) and parachloroiodobenzene (pCIB), in all proportions, from 293 K to melting point, is established. The alloys between both components differ slightly from linear behaviour, from a thermal and crystallographic point of view, according to variations in their composition. The greater isotropic nature of the crystalline expansion caused by the introduction of the bulkier component (pCIB) into that of less reticular volume (pBCB) is revealed, with respect to the alloys that only contain Br and Cl as benzene substituents.

Isomorphism of 2-methylnaphthalene and 2-halonaphthalenes as a revealer of a special interaction between methyl and halogen

The systems 2-methylnaphthalene+2-chloronaphthalene and 2-methylnaphthalene+2-bromonaphthalene belong to the exceptional group of binary systems where the formation of mixed crystals goes together with a solid–liquid phase diagram with a maximum. For these systems a thermodynamic analysis is presented which is based on new phase diagram and thermochemical data. The excess Gibbs energies, excess enthalpies, and excess entropies of the mixed crystalline state all are negative. These properties correspond to a net attraction between methyl and substituted halogen. Additional evidence of such an attraction is given by the outcome of a statistical search on intermolecular contacts, in the crystalline state of pure substances, among methyl+halogen, halogen+halogen, and methyl+methyl.

Molecular alloys in the series of para-disubstituted benzene derivatives. Part 8. The para-dichlorobenzene + para- bromoiodobenzene system

Experimental data are given for the solid-liquid equilibrium in the system (1 − X)p-dichlorobenzene + X p-bromoiodobenzene. The significance of the data is supported by a thermodynamic phase-diagram analysis.

Behaviour during thermal cycling of molecular alloys for the storage of thermal energy. II: Alloys with P-chloroiodobenzene and P-bromoiodobenzene

The p-chloroiodobenzene and p-bromoiodobenzene compounds and molecular alloys between p-dichlorobenzene, p-bromochlorobenzene, p-dibromobenzene, p-chloroiodobenzene and p-bromoiodobenzene have been characterized by thermal cycling. DSC thermal analysis have been used to determine T[sub fusion], [Delta]H[sub fusion] in order to evaluate their performance in the thermal cycling.