Mixed Dispersions of Two Antifoams

We may extend this argument to mixtures of antifoam dispersions. Here we suppose, for example, that two different antifoams are separately dispersed in the same surfactant solution and the resultant dispersions are mixed in known ratios. Again we assume that the antifoam effects are caused by single entities and that therefore the effects are not cooperative. The argument is illustrated in terms of the ratio F but could of course be equally well illustrated using the relevant foam volumes since 

FIGURE 5.4 Reduced plot of F against logio(c,/cf ° ) for thin sugar beet juice containing three unspecified different antifoams of significantly different effectiveness [13]. Foam was generated by the Bikerman method [15]. 

If Cj is the concentration of the mixed antifoam dispersion, then we must have 

The ratio F for the mixed antifoam dispersions is obviously some function of the concentration of each antifoam species so that 

If we now allow the relative effectiveness of the mixed antifoam dispersion to be adjusted to give the same value of F = F° as that of the dispersions of the constituent antifoams alone by simply adjusting the overall concentration (at constant composition), then we can write by analogy with Equation 5.1 

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