Wilhelmy hanging plate

The Wilhelmy hanging plate method (13) has been used for many years to measure interfacial and surface tensions, but with the advent of computer data collection and computer control of dynamic test conditions, its utility has been greatly increased. The dynamic version of the Wilhelmy plate device, in which the liquid phases are in motion relative to a solid phase, has been used in several surface chemistry studies not directly related to the oil industry (14- 16). Fleureau and Dupeyrat (17) have used this technique to study the effects of an electric field on the formation of surfactants at oil/water/rock interfaces. The work presented here is concerned with reservoir wettability. 

The total surface tension of liquids (7 ) is most easily determined by the Wilhelmy plate method (Adamson, 1990). Briefly, a thin rectangular plate (e.g., a chromic acid cleaned glass microscope cover slip, or an acid cleaned platinum plate) is suspended vertically from the arm of a microbalance, until it just touches the hanging plate. Upon contact with the liquid, a small additional force, or additional weight (AW), is exerted on the plate, so that (Adamson, 1990) ... 

When a citrus oil and aqueous phase are equilibrated together under static conditions for prolonged periods at 30-50°C (e.g., 12 hours), a film or precipitate is often seen at the interface. If an interfacial film forms, it is transparent and clearly visible only when the Wilhelmy plate is pulled away from the citrus oil/ aqueous phase interface. Such films appear to be continuous and are located on the oil side of the interface. They are very thin and cannot be seen on the plate or hanging from the plate once the plate is removed from the citrus oil. The film acts as though it dissolves as the plate is slowly pulled away from the interface and through the citrus oil phase. 

The film pressure is usually measured by the Wilhelmy plate method. Usually the Wilhelmy plate is a piece of absorbent paper hanging into the water subphase. The force acting on it is proportional to the surface tension. More rarely, the force on the barrier is determined directly. 

In Wilhelmy s method, the downward pull exerted by a liquid on a thin vertical glass or metal plate hanging partly immersed in the liquid and wetted by it, is measured by suspending the plate from one arm of a balance and... 

Table 1.2. Surface tensions of water in mN m , obtained by various investigations using different techniques. Temperatures in degrees Celsius. Abbreviations for methods CR = capillary rise, WP = Wilhelmy plate, DNR = Du Nouy ring, DM = other detachment method or object in the surface. HD = hanging (pendent) drop, SD = sessile drop, MBP = maximum bubble pressure DW = drop weight.

Abbreviations CR = capillary rise DM = detachment method (including Wilhelmy plate and Du Nouy ring) DW = drop weight ( stalagmometer ) HD = hanging (pendant) drop MGP = maximum gais bubble pressure SD = sessile drop. 

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