Premelting Anomalies of Some Long Chain Normal Paraffin Hydrocarbons

Abstract

The coefficients of thermal expansion of tetradecane, hexadecane, octadecane, and tetracosane have been measured continuously for considerable temperature ranges on both sides of the melting points. The increase of these coefficients in the neighborhood of the melting points is suggestive of an order-disorder mechanism for the transitions. Although the effect is observed to be larger on the solid side of the transition than on the liquid, the latter is interpreted as more significant, since the presence of impurities and the open, mosaic structure of the solid contribute largely to the increase. Likely impurities are not of the Raoult type, and do not cause appreciable variations.