The covolumes of the fused aliphatic acids from C9 to C18 and of C2, from viscosity measurements

Abstract

The results of measurements of the viscosities and molar volumes of the organic acids (C9--C1~) as functions of the temperature are reported. They are discussed in connection with the equations of Arrhenius and Batchinski.Results concerning viscosity measurements on the linear aliphatic acids C9, Ca0, Clz, C1~, Ca6 and C_as were discussed in a previous paper [1 ]. The present one deals with the covolumes (obtained from viscosity measurements by the Batchinski formula) of all the acids, odd and even, from C9 to Cls, and of C~. ExperimentalThe experimental methods are described in detail in the previous paper [1]. MaterialsFluka purum hendecanoic and tridecanoic acids and puriss, pentadecanoic and margaric acids were purified as previously [1] described; C. Erba RP acetic acid was purified by distillation following the Rabin0witsch method [2]. Results and discussionThe experimental values are collected and shown in Table 1 and Fig. 1(a-b). From the graphs log ~/ versus lIT and ~ versus Vm it is possible to obtain Eact and b V from the Arrhenius and Batchinski equations. These are listed in Tables 2 and 3. As previously described [1 ], for the even series the covolumes of these acids can be calculated on the basis of the model reported in Fig. 4 of the preceding note [1 ]. Further, for the acids Cll, C1~, C15 and C17 , the covolume bv closely corresponds to the value that can be calculated from the model under the hypothesis that the dimer rotates around the a axis, describing a cylinder; that is by = 1/2(12/2+rc)21lN.

Ultrasonic velocity, isothermal compressibility, free volume andP i/T f values in molten stearic, palmitic and lauric acids. Reflections on fusion

“…The viscosimetric data of some organic melts [2][3][4], plotted according to Batschinski [23] as n = A/(V -b), provide a covolume b, which is much greater with respect to the effective dimensions of the compound: …”

“…This method allows results to be interpreted in terms of the structure of the melts, starting from the structural model of the solid. In this note, giving ultrasonic velocity, as well as Pi, Pi/T~, fls, flu, c~ and V r values of some molten organic acids, we discuss some considerations on the link existing between fusion entropy and disorder volume on the basis of data of preceding works [2][3][4][5] or on the basis of data available in the literature on both organic and inorganic compounds. We also give an equation connecting Pi, V and T, valid in the temperature range studied.…”

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

“…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.…”

“…b = Vm~r + Vdi~ (2) Therefore, b -Vintr may be a measure of the disorder caused by the motions of the molecules and introduced at the fusion point.…”

“…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.…”