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The lattice symmetry and lattice parameters of the low-temperature solid forms I1 and I of 2-methyl-2-nitropropane (TBN), (CH,),CNO,, have been determined by X-ray powder diffraction and found to be of the orthorhombic and face-centred cubic type, respectively. The pVT data have been determined in the temperature range 228 to 353 K up to ca. 300 MPa, as well as the volume changes accompanying the phase transitions. The volume changes allow the calculation, via the Clausius-Clapeyron equation of the corresponding entropy changes. The volume changes on melting decrease markedly with increasing pressure, whereas those at the solid-solid transitions (I1 -, I and 111 + 11) exhibit a much less pronounced pressure dependence. With regard to the entropy changes, only the I1 -+ I transition shows a small dependence (decrease) on increasing pressure. The two mean parts of the entropy changes (configurational and volume-dependent terms) are discussed for each transition.

Differential thermal analysis has been performed on cyanocyclohexane (CCH), 1,2,3,4-tetrahydro-5,6-dimethyl-1,4-methanonaphthalene (TDMN), and 2-methyl-2-propanol (t-butanol) up to 300 MPa. The latter compound was also investigated dielectrically. CCH displays an ODIC phase that transforms only reluctantly to the low-temperature stable phase II. Annealing under pressure can appreciably accelerate this transformation. For all three compounds the phase diagrams were established. For CCH and TDMN also the pressure dependence of the glass transition has been determined.

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A mass-spectrometric technique for determining ion profiles through low-pressure flames (1–6 mm Hg) has been developed. Typical results are presented for hydrocarbon—oxygen flames which show that the dominant ion is H3O+ and that the concentration of C3H3+, the next most abundant ion, reaches a maximum concentration in the flames ahead of H3O+. A large number of other ions are also identified.