**Viscosity of Aqueous Solutions of Tetramethyl-,
Tetraethyl-, Tetra-n-propyl-, Tetra-n-butyl-, and Tetra-n-pentylammonium
Cyclohexylsulfamates from 293.15 K to 323.15 K **

**Cveto Klofutar,**^{1}** Jaka
Horvat,**^{2}** Marija Bešter-Rogač**^{3}
**and Darja Rudan-Tasič**^{1,*}

^{1}* Biotechnical Faculty, University of Ljubljana,
SI-1000 Ljubljana, Slovenia.
*

* Corresponding author: E-mail:

**Abstract**

The viscosities of aqueous solutions of tetramethyl-, tetraethyl-, tetra-n-propyl-,
tetra-n-butyl-, and tetra-n-pentylammonium cyclohexylsulfamate were determined
at 293.15, 298.15, 303.15, 313.15 and 323.15 K. The relative viscosity was
analysed and interpreted in terms of the *Kaminsky* equation, *η*_{r}=
1 + *Ac*^{1/2} + *Bc* + *Dc*^{2}. The
viscosity *A*-coefficient was calculated from *Falkenhagen-Dole*
theory and its temperature coefficient estimated. The viscosity *B*-coefficients
of the solutes are positive and relatively large, while their temperature
coefficients are negative and decrease with increasing molecular weight of the
solutes. The viscosity *D*-coefficient was discussed in terms of higher
terms of the long-range *Coulombic* forces and hydrodynamic effects, as
well as structural solute-solute interactions. The limiting thermodynamic
functions of activation for viscous flow of solute, i. e. the *Gibbs*
free energy, enthalpy and entropy, were evaluated using the theoretical approach
given by *Feakins et al*. From the limiting partial molar functions of
activation of the solute the contribution to the activation functions of solvent
molecules were calculated using the corresponding limiting functions of
activation for charge transport of solute ions.

**Keywords:** Viscosity data, viscosity *A*-, *B*-
and *D*-coefficients, activation parameters, cyclohexylsulfamates,
aqueous solutions