Question

7. How to increase the stability of emulsion?

8. What are the similarities and differences between emulsion and dispersion?

Answer 1

7. The term stability when applied to emulsions usually refers to the resistance of emulsions to the coalescence of their dispersed droplets.

In other words , the smaller the rate of coalescence of dispersed phase , more stable is the emulsion.

Factors that determine the increase in stability of emulsions are described as :

1. Physical nature of the interfacial film : One of the prime factors determining emulsion stability is mechanical strength of the interfacial film . Liquid crystal formation can also stabilize the emulsion . By accumulating at the interface surrounding the dispersed particles , liquid crystals surround the particles with a high viscosity region that resists the coalescence of individual droplets .

2. Existence of electrical or steric barrier to coalescence of the dispersed droplets: The presence of a charge on the dispersed droplets constitutes an electrical barrier to the close approach of two particles to each other . Thus prevents coalescence of dispersed droplets and stabilizes the emulsion .

3. Viscosity of the continuous phase : An increase in viscosity of the continuous phase reduces the diffusion coefficient D of the droplets . As the diffusion coefficient is reduced the frequency of collision of the droplets and their rate of coalescence are reduced .

4. Size distribution of droplets: The smaller the range of sizes of droplets, the more stable is the emulsion .

5. : A change in temperature causes changes in the interfacial tension between the two phases , in the nature and viscosity of the interfacial film .Thus temperature changes usually cause considerable changes in the stability of emulsions . An optimum temperature choice is therefore necessary for the stability of emulsions.