ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The pendant drop method and the capillary rise method are used to measure the interfacial tension σ of 2,6-dimethyl pyridine(2,6-lutidine)/water mixtures near the lower critical point. It is found that at temperatures 0.2 K≤(T−Tc)≤1.5 K the temperature dependence of σ is represented by a power law of the form σ=σ0 tμ (t=(T−Tc)/Tc) with μ=(1.25±0.01) and σ0=(32.4±0.6) mN m−1. The value of μ is consistent with the theoretically expected universal value of μ=1.26. At large temperature differences σ increases slower than expected by the power law. The values of the amplitude ratios Rσ,ξ+[=σ0(ξ0+)2/(kBTc)] and Rσ,A+[=(Av,0/kB)2/3(kBTc/σ0)] calculated from the experimental data [correlation length of local concentration fluctuations, ξ0+=(0.230±0.009) nm] and Av,0 (heat capacity per unit volume at constant pressure; Av,0=1.81 J cm−3 K−1) are consistent with accepted values. This indicates that the interfacial tension measurements are free from large systematic errors. The value of a2 (a, capillary constant) determined with the pendant drop method as well as with the capillary rise method agree with each other within the uncertainty of the measurements in a temperature range (T−Tc)≤7 K. The capillary rise data is analyzed by assuming that the contact angle θ of the lower water rich phase at the capillary wall is zero (θ=0). The data follows the same curve as that obtained with the pendant drop method in a temperature range (T−Tc)≤25 K. From these findings it is concluded that the water rich (lower) phase wets the wall of the glass capillary completely at least up to temperature differences (T−Tc)≤7 K. A wetting transition cannot be detected in that temperature range.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.463494
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