Thermal Expansion Anomaly Near the Critical Consolute of Triethylamine-Water

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Bani Fadel, Ranan Munier
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An-Najah National University
The dynamic shear viscosity of Triethylamine–water (or TEA–water) binary liquid mixture has been measured at temperature range 291.0- 293.0K and concentration range 0.0%- 100.0% by weight of Triethylamine. The results show, as the temperature increases the dynamic viscosity values for each concentration decreases and the anomaly in the dynamic viscosity values was observed at the critical temperature Tc= 291.6K. The critical temperature Tc= 291.6K which has been found is in agreement with the value measured by Abdelraziq (Abdelraziq, 2003). On the other hand, the dynamic viscosity value increases as the concentration by weight of Triethylamine increases until the concentration becomes Xc = 72.3%. After that the dynamic viscosity value starts decreasing. The critical value of dynamic viscosity ηc was measured at the critical temperature Tc= 291.6K and the critical concentration Xc= 72.3% and was found to be 4.816cP. In addition, the mass density of the binary liquid mixture has been measured at the same concentration range and at the same temperature range. According to these results, the density decreases as temperature increases for each concentration. Likewise, the density of the binary liquid mixture also decreases as the concentration of Triethylamine increases for each temperature. Moreover, the critical mass density ρc at the critical concentration XC= 72.3 % and the critical temperatures Tc= 291.6K was measured and found to be 0.7752(gm/〖cm〗^3 ). The isobaric thermal expansion coefficient has been also studied near the critical temperatures Tc= 291.6K and at the critical concentration XC = 72.3 %. Consequently, the critical and background isobaric thermal expansion coefficient were found to be αpc= 4x10-5K-1 and αpb= 4.304×10-3K-1, respectively. The critical amplitude of specific heat at constant pressure (atmospheric pressure) Cpc for Triethylamine–water binary liquid mixture was also calculated and found to be 3.084J/(gm.K). This value was close to the value calculated by Abdelraziq which equal to 2.58 J/(gm.K) (Abdelraziq, 2003). In addition, the value of the pressure derivative of the critical temperature along the critical line T_c^' was calculated and found to be 4.88 x 10-3(〖cm〗^3 K)/J.