Phase Polymorphism of [Cd(DMSO) 6 ](ClO 4 ) 2 Studied by Differential Scanning Calorimetry

Five phase transitions of [Cd(DMSO) 6 ](ClO 4 ) 2 have been detected by differential scanning calorimetry, namely the three reversible transitions: stable KIa ↔ stable KIb at T C4 = 242 K, due to a change of the crystal structure, metastable KII ↔ metastable KIII at T C3 = 318 K, and metastable KII ↔ overcooled K0 at T C2 = 347 K, one irreversible transition: KIa → K0 at T C1 = 376 K, and melting at T t = 465 K. From the enthalpy changes of these transitions it can be concluded that K0 is a solid rotational phase and KII and KIII are most probably solid phases with a high degree of orientational disorder. The phases K0, KII, and KIII form an enantiotropic system, but they are metastable in relation to the phases KIa and KIb in the whole temperature range, so they form the monotropic system with them

Connection between Reorientational Motions of NH3\text{}_{3} Groups and Phase Transitions in [Ni(NH3\text{}_{3})6\text{}_{6}](NO3\text{}_{3})2\text{}_{2} and [Mg(NH3\text{}_{3})6\text{}_{6}](NO3\text{}_{3})2\text{}_{2} Compounds

Quasielastic neutron scattering data for [Νi(ΝH$\text{}_{3}$)$\text{}_{6}$](ΝO$\text{}_{3}$)$\text{}_{2}$ and [Mg(ΝH$\text{}_{3}$)$\text{}_{6}$](NO$\text{}_{3}$)$\text{}_{2}$ were subjected to a new analysis. On the basis of the excess of intensity of elastic component observed in these spectra in comparison to the intensity of this component resulting from the applied reorientational model this analysis determined temperature dependence of the new "R" parameter. This parameter gives us information concerning the number of these NH$\text{}_{3}$ groups which in the [Me(NΗ$\text{}_{3}$)$\text{}_{6}$]$\text{}^{2+}$ cation reorientate with the correlation time of order of 10$\text{}^{-12}$ s. It has been ascertained that in phases I and II of both substances under study all NH$\text{}_{3}$ groups reorientate fast (R = 6ΝH$\text{}_{3}$ groups), whereas in phases III and IV only part of these groups reorientate fast (R = 3ΝΗ$\text{}_{3}$ groups - in the case of [Νi(ΝΗ$\text{}_{3}$)$\text{}_{6}$](ΝO$\text{}_{3}$)$\text{}_{2}$ and R = 2ΝΗ$\text{}_{3}$ groups - in the case of [Mg(ΝΗ$\text{}_{3}$)$\text{}_{6}$](NO$\text{}_{3}$)$\text{}_{2}$). Moreover, the temperature dependence of reorientational correlation time τ for these fast reorienting ΝH$\text{}_{3}$ groups were also determined. The remaining NH$\text{}_{3}$ groups reorientate on a much slower time scale. Both temperature dependencies: R vs. Τ and τ vs. Τ register a deep thermal hysteresis of the phase transition: phase II - phase III (Τ$\text{}_{C2}^{h}$ - T$\text{}_{C2}^{c}$ ≈ 95 K and ≈ 35 K respectively for [Ni(ΝΗ$\text{}_{3}$)$\text{}_{6}$](ΝO$\text{}_{3}$)$\text{}_{2}$ and [Mg(ΝΗ$\text{}_{3}$)$\text{}_{6}$](NO$\text{}_{3}$)$\text{}_{2}$)

The Polish school – quo vadis?

Polska szkoła ulega ciągłym przemianom. Wdrażane są kolejne reformy edukacji w różnym stopniu wpływające na kształt polskiego szkolnictwa, programy i stosowane metody nauczania. Można często odnieść wrażenie, że reforma goni reformę, a wpływ wprowadzanych zmian na poziom edukacji ma drugorzędne znaczenie. W artykule podjęto próbę oszacowania wpływu dwóch ostatnich reform na stan edukacji chemicznej w naszym kraju. Dodatkowo poddano analizie wpływ reform na popularność chemii jako przedmiotu w szkole ponadgimnazjalnej oraz jako kierunku studiów wyższych.The Polish school is subject to continuing changes. A series of educational reforms have been implemented which have affected in varying degrees the shape of the Polish school system, programmes and applied teaching methods. One can often be under the impression that reform is chasing after reform and the impact of the introduced changes on the level of education is of secondary importance. In this paper an attempt has been made to estimate the impact of the two latest reforms on the level of teaching chemistry. In addition, the paper presents the analysis of the impact of these reforms on the popularity of chemistry as a secondary school subject and as a discipline in higher education