The shear impedance, density and viscosity of the eutectic mixture NaCNS + CH3CONH2 have been measured in the temperature range 253-313 K and at the frequencies 31 and 87 MHz. The real parts of the complex impedance and of the rigidity modulus have been obtained. The relaxation region is shifted in comparison with that of the Maxwell model and is interpreted using the modified B.E.L. model. Irregularities in the real part of the mechanical impedance (around 283 K) and in the Arrhenius plot of the viscosity (around 293 K) may be attributed to changes in the liquid structure.

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The viscosities of some aliphatic acids were measured in the vicinity of the melting point with a H6ppler viscosimeter. The dependence of the viscosity on the molar volume permitted calculation of the covolume, which is compared to that obtained from structural data.The thermodynamic properties of fusion of organic aliphatic acids from C10 to Cas were dealt with in two preceding notes [1,2], in which two stages were distinguished in the fusion process: prefusion and actual fusion. The prefusion enthalpy for stearic acid represents a value of about 10 70 of the fusion enthalpy; this value decreases from stearic acid to the acids with lower molecular weights. Such an energetic value, according to Barr et al. [3 ], is involved in the rocking motions of the methylene groups in the chain.The fusion entropies of these acids were related to those of the analogous paraffins; the average fusion entropy is slightly lower in the acids, thus revealing, in comparison with the paraffins, a certain inertia induced by the dicarboxylic ring (of the dimer) on the chain.It was hypothesized that such an entropy was working to increase the width of the twisting motion of the methylene groups on the chain. The present note examines the viscosities of these acids in the vicinity of the melting point in an attempt to elucidate the structure of the melt, the viscosity being dependent on the free volume through Batschinski's formula [4], and thus to ascribe the ASfus at a precise variation of structure. Experimental MethodsThe viscosity measurements were made on a H6ppler viscosimeter manufactured by VEB Freital, DDR.The fall tube was on a 10 ~ slope with respect to the vertical of the base plane and was enclosed in a jacket through which circulated warm water, originating from an ultrathermostat with exterior circulation. The viscometer was thermostated to __+0.05 ~ .

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By employing calorimetric and cryometric methods, the melting total and the premelting enthalpies of stearic acid were measured and the phase diagrams of the solidliquid equilibria stearic acid + A (where A is an aromatic compound or a dicarboxylic acid or I~) were determined.In this paper the results of calorimetric and cryometric studies on stearic acid are reported. ExperimentalThe calorimetric measurements were performed with a Perkin-Elmer Differential Scanning Calorimeter (DSC-IB). The details of the calibration were given in previous papers [1,2]. The description of the cryometric measurements method is reported in the notes [3,4]; the crystallization temperatures of the melts were Fig. 1. Cell for the cryometric measurements of volatile substances 7