RÉSUMÉ

Mutual diffusion coefficients of the systems (Rb,Ag)Cl and (Alk,Ag)N0₃ with Alk = Li, Na, K, Rb, and Cs are reported. Experiments in the nitrate systems were performed with either holographic real-time interferometry or Savart interferometry under free-diffusion boundary conditions. Initial diffusion boundaries were created using a flowing junction cell or bottom layer cells. Mutual diffusion coefficients in the system (Rb,Ag)Cl were measured with digital image holography, a newly developed interferometric technique. Some experiments were performed with Savart interferometry as an internal consistency check.
In the nitrate systems diffusion data were collected in a temperature range from the melting points of the mixtures up to 603 K over the whole accessible concentration range. The D values are considered to be accurate to ±1-3%. The results have been correlated using Arrhenius-type equations. Furthermore the concentration dependence of the mutual diffusion coefficient at 573 K is discussed. The data are fitted to parabolas of the form D = a₂x₂²+a₁x₂+a₀, where x₂ denotes the mole fraction of the silver nitrate. For all systems, except (Li,Ag)N0₃, parameters a₂, a₁ and a₀ show a clear linear proportionality to the radii of the alkali ions. Trace diffusion coefficients are extrapolated and discussed.
Mutual diffusion coefficients in the system (Rb,Ag)Cl with x_AgCl = 0.61 were measured in a temperature range between 573 K and 748 K. The results show an Arrhenius behaviour with D = (1.37 ± 0.10) m² s⁻¹exp(-(20.7 ± 0.4) kJ mol⁻¹/(RT)).