The viscosities of some allioxides of titanium, zirconium, cerium (IV), thorium, and tin (IV) have been measured in the t e m p e r a t~~r e range 25-40' C. The liquid structure in these compounds is discussed in terms of the activation energy, free energy, and elitropy of activation for viscous flow, and the energies of cohesion and vapor~zation. INTRODUCTIONPreviously (1) we investigated the liquid-state properties of a number of germanium tetraalkoxides (alkyl orthogernlanates) in order t o establish a basis for comparison with similar properties of a number of metal alltoxides. The germanium alltoxides are monomeric whereas some of the metal alltoxides studied in this research are ltnown to be polymeric. I t was of interest, in connectioi~ with the theory of intermolecular forces in the liquid state, to study the behavior of both monomeric and polyineric metal alltoxides since these large molecules are believed to have globular or quasi-spherical structures. We now report some results on the viscosities of a number of alltoxides of the group IV metals and discuss these in conjunctioil with related properties of the liquid state. EXPERIMENTAL Preparation of the AlkoxidesThe alltoxides of titanium (2), zirconium (2), ceriuill (3), thorium (4), and tin (5) were prepared, purified, and analyzed by the previously described methods. Titanium tetraethoxide is a supercooled liquid a t room temperature but it did not change in viscosity when kept in the apparatus over 8 hours. Viscosity Meas~wementsAll-glass Ostwald visconleters were calibrated using pure benzene a t 25, 30, 35, and 40" C. The sample of alltoxide was distilled into the rigorously dried viscolneter a t 0.1 mm pressure and dry nitrogen was the11 admitted a t atnlospheric pressure. The temperature of the viscometer was coiltrolled to &O.O1° C and three separate determinations were carried out on each coi~~pound. T h e reproducibility mas of the order of 3~0.0001 p i s e s for the least viscous and 3~0.01-0.02 poises for the most viscous compouncls. The results (viscosity in poises) are presented in Table I. T h e activation energies of viscosity EVi,, (kcal/mole) were evaluated graphically fro111 the plot of log q versus l / T O I<. The free energies of activation of viscous flow AF+ (kcal/inole) were calculated from Eyring's (6) equation:The molar voluines were talten from our previous work (8) and the molar heats of vaporization from the results of vapor pressure studies (2).

The densities and surface tensions of several alkoxides of titanium, zirconium, tin, cerium, and thorium have been measured over the temperature range 25-40' and the parachors have been calculated. Analysis of the parachors by the method used for alkyl orthogermanates revealed some characteristic structural features. Parachor " contractions " in titanium n-alkoxides are consistent with the polymeric nature of these compounds and, in the monomeric tertiary alkoxides of titanium, zirconium, tin, cerium or thorium, suggest the presence of considerable intramolecular congestion accentuated by metal-oxygen bond contraction.