Analysis of Gouy Fringe Data and Comparison of Rayleigh and Gouy Optical Diffusion Measurements Using the System Raffinose (0.015 M)-KCl (0.5 M)-H2O at 25°C

Thirteen isothermal ternary diffusion expts. were done for a single compn. of the system raffinose-KCl-H2O at 25°C. Both Rayleigh and Gouy optical systems were used in all expts. for direct comparison of results from these two configurations. Various data anal. procedures are compared. Good agreement was found between the recommended results from the two optical methods, although diffusion coeffs. Dij obtained by the Rayleigh method were generally slightly lower than those obtained by the Gouy method. The sensitivity of the Dij to both exptl. error and choices of subsets of the 13 expts. is discussed. Std. errors of coeffs. are an inadequate measure of accuracy. This study has led to higher stds. for acceptability of individual expts. This system has the same mean solute concns. as the four expts. reported by P. J. Dunlop (1964), for which a test of the Onsager reciprocal relations (ORR) failed. Our diffusion results are reasonably similar to those of Dunlop. Therefore the reported failure of the ORR test probably results from errors of estg. activity coeffs. for this system rather than from diffusion data.