Soap Bubbles and Foams

Let us consider two systems pure water or a soap (detergent) solution. If pure water is shaken, then no bubbles are observed at the surface. All pure organic fluids exhibit no bubble formation on shaking. This means that as air bubbles rise to the surface of the liquid it merely exits into the air. On the other hand, if an aqueous detergent (SAS) solution is shaken or an air bubble is created under the 

Air bubble inside liquid phase— at surface bubble detaches and moves up under gravity. 

The detergent molecule forms a bilayer in the bubble film. The water in between is the same as the bulk solution. This may be depicted as follows  

Bubble at the surface forms double layer of detergent with some water in between (TLF) (varying from 10 to 100 (un). 

One of the most important roles of bubbles one finds is in the food industry (such as ice-cream champagne and beer industry). The stability and size of the bubbles determine the taste and the looks of the product. Especially, in the case of champagne, both the size and the stability of bubbles have been found to determine the impact of taste and flavor. It has been estimated that in a bottle of volume 750 mL, there will be about 50 million bubbles (if the average radius of bubbles is 0.1 mm) (Birdi, 2010a). This is a very rough estimate. However, more accurate estimates have been made by using photography of bubbles, etc. In the wine industry, much research has been made on the 

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