Fusion entropy and melt viscosity in some aliphatic hydrocarbons. Relation between fusion entropy and parameterb of the Batchinski equation

Abstract

The fusion entropy, viscosity and molar volume are measured for the following hydrocarbons: C18H~8, CxgH4o, C~0H42 and C20H40. A relation between dSfus and the parameter b of the Batchinski equation is given for these compounds and for others previously studied. By employing the calorimetric and viscometric data found in the literature for ionic melts, a similar relation is found to hold for molten salts.In two previous papers [1,2] and at a recent congress [3] it was pointed out that some organic melts follow the Batchinski equation [4]; in fact the fluidity is a linear function of the molar volume:From the experimental straight line ~ =f(V) the b values were obtained for several acids, two esters and two ethers. Generally b is higher than the intrinsic volume and lower than the molar volume. For the acids [1, 3] a geometrical form of volume b was found, whose packing gives the molar volume approximatively.The hypothesis was put forward that b is generally not the intrinsic volume, but the volume not utilizable for the flux owing to the motions of the molecules, i.e.Therefore, b -Vintr may be a measure of the disorder caused by the motions of the molecules and introduced at the fusion point.In this note a relation between the fusion entropy and V~is is examined for the studied compounds [1][2][3]; in addition, four hydrocarbons are investigated and the relation is also verified for them. Finally, the relation is extended to a wide class of molten salts (alkali metal halides and nitrates) by employing data from the literature.