--%>
Assignment Help - homework help

What are emulsions?Describe its preparation and tests.

Emulsions are colloidal solutions in which disperse phase as well as dispersion medium is both liquids. Emulsions can be broadly classified into two types:


(i) Oil in water (O/W type) emulsions: in this type of emulsions, oil acts disperse phase and water acts as dispersion medium. Some examples of this type of emulsions are milk, vanishing cream, etc.

(ii) Water in oil (W/O type) emulsions: in this type of emulsions, water acts as disperse phase and oil acts as dispersion medium. Some examples are cold cream, butter, cod liver oil etc.

The two types of emulsions can be interconverted simply by changing the proportion of the dispersed phase and dispersion medium. For example, O/W type of emulsion can be converted W/O type by adding excess of oil to O/W emulsion.

Detection of emulsions

The below mentioned tests may be applied to distinguish between the two types of emulsions:

(i) Dye test: to the emulsion some oil soluble dye is added. If the background becomes coloured, the emulsion is water in oil type and if the droplets become coloured, the emulsion is oil in water type.

(ii) Dilution test: if the emulsion can be diluted with water, this indicates that water act as the dispersion medium and the emulsion is of oil in water type. If the added water forms a separate layer, then in that case the emulsion is water-in-oil type.

Preparation of emulsions

The process of making an emulsion known as emulsification. Emulsions may be obtained by vigorously agitating a mixture of both the liquids. But this gives an unstable emulsion the dispersed drops at once come together and form a separate layer. To stabilize an emulsion, the addition of a small quantity of the third substance known as emulsify agent or emulsifier is essential. The emulsified agents form an interfacial film between suspended particles and the dispersion medium. For example, soaps and detergents are frequently used as emulsifiers. They coat the drops of an emulsion and check them from coming together thereby establishing the emulsion. The principle emulsifying agent for W/O type emulsions are heavy metal salts of fatty acids, long chain alcohols, lamp black, etc. the emulsifying agents used for O/W type emulsions are proteins, gums, natural and synthetic soaps, etc.

   Related Questions in Chemistry

  • Q : F-centres If a electron is present in

    If a electron is present in place of anion in a crystal lattice, then it is termed as: (a) Frenkel defect  (b) Schottky defect  (c) Interstitial defects (d) F-centre Answer: (d) When electrons are trapped in anion vacancies, thes

    		•
  • Q : Finding strength of HCL solution Can

    Can someone please help me in getting through this problem. 1.0 gm of pure calcium carbonate was found to require 50 ml of dilute  HCL for complete reaction. The strength of the HCL  solution is given by: (a) 4 N  (b) 2 N  (c) 0.4 N  (d) 0.2 N

    		•
  • Q : Which is polar HCl or HF Which one is

    Which one is polar HCl or HF?

    		•
  • Q : Explain the process of adsorption of

    The extent of adsorption of a gas on a solid adsorbent is affected by the following factors: 1. Nature of the gas Since physical adsorption is non-specific in nature, every gas will get adsorbed on the

    		•
  • Q : P block bif3 is ionic while other

    bif3 is ionic while other trihalides are covalent in nature

    		•
  • Q : Explain Photoelectron Spectroscopy. The

    The energies of both the outer and inner orbitals of atoms and molecules can be determined by photoelectron spectroscopy.Energy changes of the outermost or highest energy electron of molecules were dealt with here in a different passion. The energies of ot

    		•
  • Q : Molar mass lculwhat is the equation for

    lculwhat is the equation for caating molar mass of non volatile solute

    		•
  • Q : Solution problem What is the correct

    What is the correct answer. To made a solution of concentration of 0.03 g/ml of AgNO3, what quantity of AgNO3 must be added in 60 ml of solution: (a) 1.8  (b) 0.8  (c) 0.18  (d) None of these

    		•
  • Q : Describe First Order Rate Equation The

    The integrated forms of the first order rate equations are conveniently used to compare concentration time results with this rate equation. Rate equations show the dependence of the rate of the reaction on concentration can be integrated to give expressions fo

    		•
  • Q : Reducible Representations The number of

    The number of times each irreducible representation occurs in a reducible representation can be calculated.Consider the C2v point group as described or Appendix C. you can see that (1) sum of

    		•