Further results are reported for ferric dithiocarbamate complexes Fe(S&NRZ)s, which lie at the crossover between high-spin (sextet) and low-spin (doublet) states. Magnetic measurements made over a range of temperatures and pressures are used to estimate E, the separation of the zero-point energies of the 2Tz and BA1 states, and AV, the difference between the volumes of the 6A1 and 2 T~ states. The values of E extend over a large range, both positive and negative, for various complexes, while A V is generally 5-6 cm3/mol; this corresponds to an increase of 0.1 A of the Fe-S bond lengths in passing from the 2 T~ to the 6 A~ state. The compounds may be divided into four distinct classes on the basis of their solution magnetic moments (peff); in order of decreasing petf values (and hence decreasing population of the EA^ state), these are: (1) the pyrrolidyl complex where NRz = pyrrolidyl, peff = 5.8 BM; (2) the N,N-di-n-alkyl complexes, peff = 4.3 BM; (3) the N-alkyl, N-aryl complexes, peff = 3.5 BM; (4) the N,N-di-sec-alkyl complexes, peff = 2.5 BM. The RNR angle in the Fe(SzCNR2)s complexes is expected to increase from class 1 through to 4, with a corresponding change in the C-N bond order, which is expected to affect ligand field strength (A) and pelf. Comparisons of the electronic spectra of complexes falling into the various classes and the pressure dependence of the spectral positions and band intensities are used in the assignment of electronic transitions. From the tentative spectral assignments are estimated values of the ligand field strengths and the electronic pairing energies ( r ) , and these are shown to obey the necessary inequality for the crossover situation: A(high spin)

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Liquid-vapour equilibrium data for the system benzene-n-heptane have been measured at intervals over the whole composition range at 60 and 80 �C. and for equimolar mixtures at 60, 70, and 85 �C. The changes in the thermodynamic functions on mixing, both at constant pressure and at constant volume, have been calculated. The values of these changes on mixing at constant volume have been compared with values predicted from component properties. The conditions for azeotrope formation in this system have been defined.

The stability constants and absorption coefficients of x-x charge transfer complexes were measured in solution at pressures up to 6000atm. The donors used were hexamethylbenzene, benzene, naphthalene, anthracene, and pyrene, the acceptors tetracyanoethylene, s-trinitrobenzene, 2,4,6trinitrochlorobenzene, and chloranil. The stability constants increased with pressure in every case and the volumes A V of formation of the complexes from their components, varied between -2 and -12 ml mole-l. The pressure changes in K and ~V C T can be interpreted in terms of shortening of the charge-transfer bond. For complexes of known crystal structure values of A V calculated for the solid agree with the values found in solution.