DuNouy ring method

Several other methods for determining 7 —notably, the maximum bubble pressure, the drop weight, and the DuNouy ring methods (see Section 6.2) —all involve measurements on surfaces with axial symmetry. Although the Bashforth-Adams tables are pertinent to all of these, the data are generally tabulated in more practical forms that deemphasize the surface profile. 

RH and at 25°C. using the sessile drop method. Surface tensions were measured at 25°C. using the duNouy ring method. Unless otherwise noted in the text, the contact angles were reproducible to 2° and the critical surface tensions to 0.5 dynes/cm. 

Surface Tension. Measurements were carried out by the duNouy ring method, and the corrections of Harkins and Jordan (12) were applied. Aging effects in the measured surface tensions were negligible. Each surface tension point corresponded to a solution individually prepared by weighing. 

FIGURE 1.12 Schematic diagram of the DuNouy ring method for measuring interfacial tension. 

The surface tension of the samples was determined by a DuNouy ring method using a KSV Sigma 70 tensiometer (Braumann, Germany). The equipment is useful for determination the dynamic surface tension of liquids, the wetting contact angle and the water uptake or swelling of solid samples. 

C Naggiar [44], radii of curvature (drop profile m od) D Schwarz and Moseley [9], DuNouy ring method E Krishnaswamy and Shashidhar [17], pendant drop method. 

Ring = DuNouy ring method RC = radii of cur iture (drq) profile method) ... 

Aqueous viscosity was measured at room temperature with a Brookfield and Ubbelohde viscometer. Intrinsic viscosities were measured by a five-point dilution method no shear-rate corrections were made for the data. Interfacial tension was measured with a DuNouy ring tensiometer against toluene at various polymer concentrations. The formulations used to evaluate the HMHECs for latex paints have been described elsewhere (5). 

The interfacial tension, y, in the Gibbs adsorption equation is used for equilibrium conditions as bitumen components are adsorbed. Measurement techniques available are extensive. Some of these methods are duNouy ring, maximum bubble pressure, drop volume, Wilmhelmy plate, sessile drop, spinning drop, pendant drop, capillary rise, oscillating jet, and capillary ripples. These and many others are referenced extensively by Malhotra and Wasan (153). These authors also showed that there is no correlation between emulsion stability and interfacial tension. The nature of the film dominates stability. Some relationships between interfacial tensions and crude oil properties follow. 

Employing different methods always means different solid-nematic intoractions which are particularly dominant for the methods of capillary height, DuNouy ring, Wilhelmy plate and sessile drop [28]. In fact, even under identical experimental conditions, the different history of the nematic samples can lead to a considerable dispersion of the data [57,58]. The effect of impurities is the most frequently... 

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