VAPOR-PRESSURE OF 4-METHYLPYRIDINE (MEPY) OVER [NI(MEPY)(4)(NCS)(2)]CENTER-DOT-GAMMA(MEPY) AND [CU(MEPY)(4)(NCS)(2)]CENTER-DOT-2 3(MEPY) CLATHRATES DURING THEIR DISSOCIATION/

Strain measurement and quasiequilibrium thermogravimetry were used to study the dissociation processes of two clathrates, [Ni(MePy)(4)(NCS)( 2)].(MePy) and [Cu(MePy)(4)(NCS)(2)]. 2/3 (MePy), accompanied by the l iberation of MePy into the gaseous phase. In the Ni clathrate dissocia tion process in the temperature range 298-368 K the liberated MePy was redistributed between the solid clathrate and gaseous phases; The MeP y vapour pressure over the clathrate is a function of temperature and the guest content y, which agrees with the presence in the MePy-[Ni(Me Py)(4) (NCS)(2)] system of a wide range of beta-clathrate solutions, [ Ni(MePy)(4)(NCS)(2)]. y(MePy). The same methods used to study the Cu c lathrate dissociation resulted in conclusions different from those obt ained for the dissociation process of the above clathrate: the process is described by the equation [Cu(MePy)(4)(NCS)(2)]. 2/3(MePy)(solid) = [Cu(MePy)(2)(NCS)(2)](solid) + 2 2/3(MePy)(gas); the temperature dep endence of the MePy vapour pressure over the solid sample does not dep end on its composition, which points to the absence from the system of solid solutions based on the clathrate. Standard changes of the entha lpy, entropy, and isobaric-isothermal reaction potential for the tempe rature range 292-325 K are equal to 178.5 +/- 1.7 KJ (mole of clathrat e)(-1), 463 +/- 5.6 J (mole of clathrate)(-1) K-1, and 40.4 +/- 2.4 kJ (mole of clathrate)(-1), respectively.