Apparent Molar Volume and Apparent Molar Expansibility of Tetraethyl-, Tetra-n-propyl-, Tetra-n-butyl-, and Tetra-n-pentylammonium Cyclohexylsulfamates in Aqueous Solution†
Cveto Klofutar, Jaka Horvat and Darja Rudan-Tasič*
Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000
Ljubljana, Slovenia
E-mail: darja.rudan.tasic@bf.uni-lj.si
Abstract
The apparent molar volume of tetraethyl-, tetra-n-propyl-, tetra-n-butyl, and
tetra-n-pentylammonium cyclohexylsulfamates was determined from the density data
of their aqueous solutions at 293.15, 298.15, 303.15, 313.15, 323.15 and 333.15
K. From the apparent molar volume the partial molar volume of the salts and
water was determined. The limiting apparent molar volume and apparent molar
expansibility were apportioned into their ionic components. The limiting
apparent molar volume of the salts was found to be a linear function of the
cation molecular weight. The partial molar ionic volumes at infinite dilution
were treated by a model proposed by Marcus. From the second derivative of the
limiting apparent molar volume with temperature it was found that the
investigated solutes behave as structure-making ones in water. The packing
density of the ions in solution were evaluated and compared with the
corresponding data for tetra-n-alkylammonium halides. The density of aqueous
solutions of the investigated salts can be adequately represented by an equation
derived by Redlich.
Keywords: Density data, partial molar volume, expansibility, cyclohexylsulfamates, aqueous solutions.