Tensioning: advantages disadvantages

In summary, the advantages of this technique are that (i) it is relatively quick, easy, and inexpensive to set up, (ii) it is a static method (the interfacial area is not changing as the measurement occurs (see Section 1)), and (iii) although most commonly used for liquid/vapour surface tension measurements, it can also be used to measure liquid/liquid interfacial tensions. The disadvantages are that (i) a relatively large amount of the solution of interest is required, (ii) the results depend on a contact angle that is usually difficult to measure (and thus one usually must trust that it is equal to zero), and (iii) for improved accuracy, theoretical corrections to the ideal case are needed. 

In addition to the methods discussed here and in Section 6.2, there are a few other methods for measuring surface tension that are classified as dynamic methods as they involve the flow of the liquids involved (e.g., methods based on the dimensions of an oscillating liquid jet or of the ripples on a liquid film). As one might expect, the dynamic methods have their advantages as well as disadvantages. For example, the oscillating jet technique is ill-suited for air-liquid interfaces, but has been found quite useful in the case of surfactant solutions. A discussion of these methods, however, will require advanced fluid dynamics concepts that are beyond our scope here. As our primary objective in this chapter is simply to provide a basic introduction to surface tension and contact angle phenomena, we shall not consider dynamic methods here. Brief discussions of these methods and a comparison of the data obtained from different techniques are available elsewhere (e.g., see Adamson 1990 and references therein). 

List a few methods for the measurement of surface tension and contact angle. Discuss the basic principles involved in each method. What are the experimental advantages and disadvantages in each case ... 

Harkins remarked that the history of the methods [used for the determination of surface tension] may be described as a comedy of errors when experimental errors were avoided, the calculations were based on wrong theory or vice versa, so that in practically all the best work between 1896 and 1916 errors of 3 per cent were made. He gave a table showing the relative advantages and disadvantages of the different methods. 

The connection with older ideas about reduction will be obvious [SI] and [S2] are the generalized successors of the "bridge laws" or "linking propositions" that limit the relation to a token-token instead of a type-type relationship. The hope was that supervenience relations would have all the advantages of reduction with no disadvantages. Reduction has the advantage that it explains why events are not causally overdetermined. The disadvantage of this picture is that it seems to undermine the autonomy of the S-discourse unduly. The literature on supervenience is dominated by this tension between determinacy and autonomy. 

From the previons sensitivity resnlts and discnssions, we can see that phase type is very important in determining the hnal oil recovery. Table 8.16 lists some advantages and disadvantages of three types of microemulsion systems. The highest oil recovery conld be from a type II(-), type III, or type II(+) system. Not only IFT, bnt many parameters, especially relative permeabilities, individnally or in combination, may make any of type II(-), type HI, and type II(+) microemnlsion systems the optimnm type. This is different from the conventional approach that focnses on interfacial tension as the determining parameter and conseqnently that the optimum phase type is, necessarily, type III. 

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