Ising criticality viscosity

Kleemeier, M., Wiegand, S., Derr, T., Weiss, V., Schroer, W., and Weingartner, H. Critical viscosity and Ising-to-mean-field crossover near the upper consolute point of an ionic solution. Ber. Bunsenges. Phys. Chem., 1996, 100, p. 27-32. 

In the literature there have been repeated reports on an apparent mean-field-like critical behavior of such ternary systems. To our knowledge, this has first been noted by Bulavin and Oleinikova in work performed in the former Soviet Union [162], which only more recently became accessible to a greater community [163], The authors measured and analyzed refractive index data along a near-critical isotherm of the system 3-methylpyridine (3-MP) + water -I- NaCl. The shape of the refractive index isotherm is determined by the exponent <5. Bulavin and Oleinikova found the mean-field value <5 = 3 (cf. Table I). Viscosity data for the same system indicate an Ising-like exponent, but a shrinking of the asymptotic range by added NaCl [164],... 

In the AOT-water-oil system, when the temperature is increased sufficiently a cloud point (critical point) is reached. At temperatures well below this transition temperature the viscosity data are in agreement with a simple hard-sphere model. Upon approaching the critical point one first notices a relatively moderate increase of viscosity by about a factor of 4 followed by a critical divergence of viscosity very close to the cloud point. The critical divergence of such a system (with decane as oil) at the critical temperature was studied and was shown to scale almost Ising-like according to rj [ Tc - T)/Tc] with a critical exponent of 0.03 [69]. 

By choosing the right electrode, pH meter, and accessories, the analyst can build a dedicated system for his or her application. A system capable of giving accurate, repeatable results time after time is critical, especially for difficult high-viscosity solutions. Measuring parameters as diverse as pH, ISE, conductivity, redox, and dissolved oxygen, the electrochemical meters olfer great ffexibility to measure dilferent properties in polymeric solutions. 

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