Ring method, du Nouy

Figure D3.6.1 General principle of direct force-transducer-based tensiometers (Wilhelmy plate and/or du Nouy ring method). I/O is input/output.

STATIC INTERFACIAL TENSION DETERMINATION AT A LIQUID/GAS INTERFACE BY THE DU NOUY RING METHOD... 

Static interfacial tension analysis du Nouy ring method, 635-636,640-641 vs. dynamic tension, 632 (table)... 

The chemistries of commercial oil vehicles vary with respect to the ratio of aromatic, paraffinic and cycloparaffinic carbon (generally about 20, 40, and 40 percent, respectively), degree of oxidation, and amount and character of impurities. The surface energies of the high and low viscosity ink vehicles shown in Figure 8 were 31.3, and 26.0 mN/rn, respectively (as measured by the Du NoUy ring method). 

Figure 6.4 Liquid surface tension determination by the Du Nouy ring method A maximum upward pull...

Wilhelmy Plate Method A method for determining surface or interfadal tension on the basis of measuring the force needed to pull an inert plate, held vertically, through an interface. Also termed the Wilhelmy slide method. See also du Nouy Ring Method. 

The Du Nouy Ring Method A ring with perimeter L is immersed in to a liquid and then lifted up. The maximum pull exerted on the ring by the surface tension forces is measured (see Fig. 7a). At the maximum puU the force vector will be exactly parallel to the direction of motion and the contact angle will be zero. The surface tension is then calculated from y = F IL, where is the maximum force during the lift off. A correction for the weight of the volume of... 

Surface Tension, Capillarity, and Contact Angle, Fig. 7 Surface tension measurement, (a) Du Nouy ring method, (b) Wilhelmy plate method... 

Effects of anion on surface tension. Surface tension measurements by the du Nouy ring method kept the type of cation constant while the anions were varied to include [BMIM][Bp4], [BMlM][PFg], BMlM][Tf2 N], and [BMIMJpFjSO ] and four additional cation-anion pairs. The dry ionic liquids showed the expected decreasing trends in surface tension with increasing temperature for each ionic liquid cation-anion series [5]. Increasing anion size appeared to correlate with a decrease in surface tension of the ionic liquid - as noted in reference [34]. 

Equation (2.7) shows the relationship for the calculation of surface tension by the du Nouy ring method. In this equation, Pj is the total force on the ring which is measured, is the weight of the ring, R is the radius of the ring, and is the ideal surface tension. In practice, a meniscus correction factor is required because the size and the shape of the surface inside and outside the ring are not the same. Therefore, surface tension must be... 

Surface tension of liquids can be measured by either of the two methods static and dynamic. The static methods are based on the assumption that the liquid has attained surface equilibrium. For pure liquids and solutions of crystalloids the process of attainment of equilibrium is very fast and the static methods are best suitable. But for colloidal solutions a considerable time is required to reach the equilibrium state and therefore the dynamic methods of measuring surfacf tension are preferred. The dynanJc methods measure the tension of a liquid before the surface film has had time to form. TTiere are other methods too which fall between the static and the dynamic methods. Among the static methods, the most commonly used ones are (0 the capillary rise method, (ip the du Nouy ring method, (Up the Wilhelmy balance method, and (iv) the drop-weight method.,... 

The dynamic process of adsorption of emulsifiers and the equilibrium state of the interfacial film can be measured by the change in interfacial tension as a function of time. Dynamic interfacial tension techniques exist that measure without disturbing the interface. Various such techniques to measure interfacial tension have been reported in the literature (Addison and Hutchinson, 1949 Padday and Russel, 1960). The Wilhelmy plate technique is preferred over other techniques because the values obtained are more accurate than those obtained using other techniques such as the capillary rise or du Nouy ring methods (Padday and Russel, 1960). In the latter two methods, the long equilibration time (3-60 hours) and difficulties in accurately positioning the... 

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