The crystal nucleation behavior of some normal alkane liquidsmdash;C16H34, C17H36, C18H38, C24H50, and C32H66mdash;was investigated by the droplet technique. The relative undercoolings, 1mdash;lgr;, (i.e., the actual undercooling in units of the absolute melting temperature) at which the crystal nucleation frequency in these liquids becomes 107cmmdash;3secmdash;1are 0.037 to 0.043, and almost an order of magnitude smaller than those for simple molecular substances. Crystal nucleation frequencies in droplets of C17H36and C18H38samples of very high purity were determined quantitatively. The frequencies were proportional to droplet volume and increased by a factor of 5000 to 8000 per 1deg; decrease in temperature. The results are satisfactorily described by the classical nucleation theory with values of the crystal nucleus hyphen; liquid interfacial tension sgr;, 7.2 erghyphen;cmmdash;2for C17H36and 9.6 erghyphen;cmmdash;2for C18H38. The experimental prehyphen;exponential factors in the nucleation expression agree with the theoretical values to well within the experimental uncertainty. The small relative undercooling and the weak glasshyphen;forming tendency in the highhyphen;molecular weightnhyphen;alkane liquids is satisfactorily explained by the hypothesis of nucleation of small segments of molecules.
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