The densities and viscosities of the methyl esters of hexanoic, heptanoic, oetanoic, decanoic and dodecanoic acids were determined at temperatures ranging from 10 to 80~ at 5~ intervals. The densities of the methyl esters vary linearly with temperature. When fluidities were plotted against molal volumes of the esters, smooth curves were obtained. Intrinsic volumes were determined by extrapolation to zero fluidity. Based upon Hildebrand's equation, the B values, which represent a measure of the molecules resisting transport of momentum, were calculated for each ester and found to be exponentially related to the temperatures. A modified equation relating the fluidity with temperature was formulated. Excellent agreement was obtained between calculated and experimental fluidities.We report here the densities and viscosities of five pure methyl esters of n-alkanoic acids at 15 temperatures and our attempt to correlate the viscosity with the temperature by using a modified form of Equation 1.
EXPERIMENTAL PROCEDURESAnalytical reagent-grade methyl esters of C6 to C12 fatty acids with better than 99% purity from Sigma Chemical Ca (St. Louis, MO) were redistilled and dried over molecular sieve before use.The density and the viscosity were determined with a 10-mL flask-type pycnometer and an Ubbelohde viscometer, respectively. The details were described previously (7).
The densities of some pure methyl and ethyl esters ofn‐fatty acids were determined at temperatures between 10° to 80°C. The molal volumes of these esters and the long‐chain fatty acids were correlated with temperature and chainlength. The reciprocals of the average methylene contribution at long‐chain and the end group contribution to the molal volumes were found to be linear functions of the temperature. With the introduction of a correction term to account for mutual interaction of the end groups, three equations, one for each of the esters and the acids, were developed. These equations were used to calculate the molal values of the acids with carbon numbers up to 30 and up to 20 for the esters at temperatures ranging from 10° to 100°C. Excellent agreements were obtained between the molal volumes calculated by the equations and those obtained from the literature and experimental data.
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