Temperature dependence of partial molal volume at infinite dilution for two macrocyclic aminals in aqueous solution between 275.15 and 278.15K


L. Blanco1 and J. Clavijo1

1Departamento de Química, Universidad Nacional de Colombia, Bogotá, Colombia

Keywords: aqueous solution
property: partial molal volume, infinite dilution
material: macrocyclic aminals

The search for solutes that influence the estructure of liquid water still goes on in many laboratories. The macrocyclic aminals 1,3,5,7-tatrazatricyclo(3.3.1.1.3,7) decane (HTMT), and 1,3,6,8-tatrazatricyclo(4.4.1.1.3,8) dodecane (TATD) are apolar, globular molecules that are quite soluble in water [1,2]. These properties make them a good case of study. In our laboratory a program to measure some of their properties in aqueous solution has been going on for a few years. Some of the work has been published already [1-3] and some more is underway. At this time we want to report the temperature influence on partial molal volumes at infinite dilution in a narrow range that includes the temperature of maximum density. Densities of solutions were measured using a magnetic float technique that has been described elsewhere [4]. Using the proper temperature control and all other precautions, the repeatability of the density measurements was found to be between 5.exp10-7 and 2.5.exp10-6 g.expcm-3. Measurements were made for eight concentrations from near 0.0010 to approximately 0.2000 molal for solutions of each of the two substances. As it has been found in other works the density vs concentration graphs show two regions. Following earlier treatments of data, we extrapolated the linear region to get the apparent molal volume at infinite dilution. The tendencies of the calculated values found are interpreted in terms of structure making and structure breaking effects and also using Hepler’s criteria [5].

References
  1. L.H. Blanco, N. R. Sanabria, M. T. Davila, Thermochim. Acta.. 450, 73 (2006)

  2. L.H. Blanco, N. R. Sanabria. J. Chem. Eng. Data. 52, 2288 (2007)

  3. L.H. Blanco, M. T. Davila. Fluid Phase Equilibr. 293, 237 (2010)

  4. L.H. Blanco, E. F. Vargas. Instr. Sci. Techn. 32, 13 (2004).

  5. L. G. Hepler. Can. J. Chem. 47, 4613 (1969).

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