Harkins spreading coefficient

A useful index for measuring the spreading of a liquid on a solid surface is the Harkin spreading coefficient 5, (28), which is the change in tension when solid/liquid and liquid/air interfaces are replaced by a solid/air interface ... 

In discussing wetting, the Harkins spreading coefficient deserves men-tion." If a liquid is to spread on a solid, then the work of cohesion of the liquid must be less than the work of adhesion of the liquid on the solid. Thus for spreading to occur, the spreading coefficient, 5h, defined by Eq. 

Harkins spreading coefficient of a hqnid on another, ionic strength of a solution of ions, ionic strength in relation to molality valnes. moments of inertia. 

Interfacial tensions are also used to calculate the spreading for different interfaces. Spreading of one liquid in another immiscible liquid (or solid) can be expressed via the Harkins spreading coefficient. 

When a drop of liquid is placed on another liquid with which it is immiscible, its wetting is quantified by the Harkins spreading coefficient (A = air, W = water, O = oil) ... 

The Harkins spreading coefficient is a tool for determining whether one liquid will spread upon another, for example, oil on water. If S is positive, then the two interfaces have together lower energy than the water-air interface and thus we have spreading -and the opposite (non-spreading) if 5 is negative. 

Starting from the definition of the Harkins spreading coefficient S. show that the spreading coefficient can be equivalently given as the difference between the work of adhesion of oil (o) and water (w) and the woik of cohesion of oil (o) ... 

Harkins spreading coefficient (for f W4 (fo/t + Yow) = Can be applied both to liquid-liquid and... 

The decrease in free energy taking place when the oil spreads over an area of one sq. cm. is evidently o-a— cti + ctiz] and may be taken as a measure of the tendency of the oil to spread, a point first noted by W. B. Hardy and to the value of which the name spreading coefficient has been applied by Harkins. 

In the following table are given a few values, chiefly from the data of Harkins, of the spreading coefficients for a number of liquids which spread,upon water and for liquids which do not spread but form lenses, in this latter case the value of cr [o + o- z is evidently negative. 

Harkins WD, Feldman AJ (1922) Films - spreading of liquids and the spreading coefficient. J Am Chem Soc 44 2665-2685... 

Harkins defined the term initial spreading coefficient (for the case of oil on water) as... 

Harkins gives the following typical values of spreading coefficients any positive value causes spreading to occur on a clean surface while a high positive value permits spreading against the surface pressure of a considerable amount of contamination. 

In accordance with Harkins definition the following spreading coefficients are distinguished initial s, semi-initial s and final (equilibrium) se spreading coefficients... 

The primary thermodynamic consideration involved is that of welting or spreading. For the adhesive to achieve the molecular closeness to the substrate required for strong van der Waals forces to develop, it must wet the substrate. In order for this to happen, the spreading coefficient S (Harkins, 1941) as defined by the equation... 

The antifoaming action can be rationalised [28] in terms of the balance between the entering coefficient E and the Harkins [29] spreading coefficient S, which are... 

Harkins [8, 9] defined the spreading coefficient as the work required to destroy unit area of SL and LV and leaves unit area of bare solid SV,... 

In order to analyze the spreading process, Harkins introduced the concept of S, the spreading coefficient in 1919. He realized that spreading occurs if the surface tension of the underlying liquid surpasses the sum of the tensions of the interface and the top liquid. When the converse condition occurs, the drop assumes and retains a lens shape. Harkins defined the initial spreading coefficient, S,, 2, for a liquid (1) on another liquid (2),... 

Equation (468) is equivalent to Harkins s equation (Equation (460)). However, we must also consider the effect of the mutual saturation of the liquids on the equilibrium spreading coefficient, S /2. After the initial contact of oil and water molecules [or liquids (1) and (2)], they will become mutually saturated within each other after a while, so that yw will change to y o) and y0 to y)(W). At equilibrium, Equations (460) and (461) turn into... 

According to Harkins, the spreading coefficient Aj. of liquid (component i) on solid (component j)... 

Harkins soon afterwards [55-58] developed fully the usefulness of their concept, named S the "initial spreading coefficient," and from it derived the two relations... 

Here is the reversible work of cohesion of the liquid from the Dupre equation for a liquid-liquid interface it is simple to show that Wc is twice the liquid surface tension. Equations 8 and 9 are especially suggestive about the physical cause of spreading however, like Equation 1, they are deceptively simple. As Harkins pointed out, an "initial value" of the spreading coefficient exists for the condition that spreading can initiate a "final coefficient" exists for the conditions that once spreading has occurred the liquid can remain spread. It turns out that much experimental information is needed to determine the final spreading coefficient. 

On the other hand, we can use the of n-heptane on graphite (58 dynes per cm.) measured by Loeser [14] and assume that it equals the spreading coefficient, S (as did Harkins [13]), which leads to... 

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