The thermal behavior of amorphous hydrated zirconium oxide and its coprecipitates with other oxides was studied.Solid solution with a limit of solubility seems to exist in the amorphous coprecipitates. A relation with the hightemperature solid solution was established. The structure of the amorphous zirconia was studied by X-ray and neutron diffraction; a thin plate model related to the structure of tetragonal zirconia is proposed. Heating the precipitates in an oxygen-free atmosphere produced a black nonstoichiometric oxide and stabilization of the tetragonal form.

In tricalcium silicate and its solid solutions six modifications were established: one rhombohedral (R), two monoclinic (MI, MII), and three triclinic (TI, TII, TIII). All these forms are rhombohedral or pseudorhombohedral and extremely similar; the variations in the X‐ray diagrams and the transformation enthalpies are minute. Only three of the five transitions were observed by both X rays and DTA: TI‐TII (600°), TIII–MI (980°), and MI–MII (990°); one was established by DTA (TII–TIII, 920°) and one by X rays only (MII–R, 1050°C). This scheme of polymorphism is compared critically with results of other authors, and the nature of the various displacive transformations is discussed. X‐ray and DTA investigations of solid solutions of Ca3SiO5 with Al2O3 and ZnO established the phase relations as functions of temperature and composition. With Al2O3, two modifications (TI and TII) were stabilized; and with ZnO, five polymorphs (TITII, MI, MII, and R). With both pure C3S and the solid solutions, the results are consistent and have a close bearing on the constitution of alites in portland cement clinker.

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Several experimental results and discussions have previously been reported concerning the thiourea-cyclohexane inclusion compound (TCIC). They were obtained using nitrogen-14 NQR, proton wide-line NMR, relaxation time measurements, differential thermal analysis, and x ray diffraction methods. In the present paper new results of wide-line proton NMR on partially deuterated samples (thiourea-d4-cyclohexane) and a detailed interpretation of x-ray diffraction patterns are presented; the discussion leads to a better description of the behavior of the host lattice and guest molecules as the temperature of the sample is increased from −196°C to room temperature. The proposed model is also compared to that obtained for urea-trioxane, a similar inclusion compound described by the authors in an other paper.