--%>
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 : What is protein in Chemistry Illustrate

    Illustrate what is protein in Chemistry?

    		•
  • Q : Numerical The volume of water to be

    The volume of water to be added to 100cm3 of 0.5 N N H2SO4 to get decinormal concentration is : (a) 400 cm3 (b) 500cm3 (c) 450cm3 (d)100cm3

    		•
  • Q : Relationship between Pressure and

    The pressure-temperature relation for solid-vapor or liquid vapor equilibrium is expressed by the Clausis-Clapeyron equation.We now obtain an expression for the pressure-temperature dependence of the state of equilibrium between two phases. To be specific,

    		•
  • Q : Problem on moles of solution The number

    The number of moles of a solute in its solution is 20 and total no. of moles are 80. The mole fraction of solute wil be: (a) 2.5 (b) 0.25 (c) 1 (d) 0.75

    		•
  • Q : Concentration of urea Help me to go

    Help me to go through this problem. 6.02x 1020 molecules of urea are present in 100 ml of its solution. The concentration of urea solution is: (a) 0.02 M (b) 0.01 M (c) 0.001 M (d) 0.1 M (Avogadro constant, N4= 6.02x 1023mol -1)<

    		•
  • Q : Molarity what is the molarity of the

    what is the molarity of the solution prepared by dissolving 75.5 g of pure KOH in 540 ml of solution

    		•
  • Q : Molarity of acid solution If 20ml of

    If 20ml of 0.4N, NaoH solution completely neutralises 40ml of a dibasic acid. The molarity of the acid solution is: (a) 0.1M (b) 0.2M  (c) 0.3M (d) 0.4M Choose the right answer fron above.

    		•
  • 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 : What is cannizaro reaction? Explain

    Aldehydes which do not have  -hydrogen atom, such as formaldehyte and benzaldehyte, when heated with concentrated (50%)alkali solutio

    		•
  • Q : What is adsorption and its examples. In

    In a liquid a solid substance a molecule present within the bulk of the substance is being attracted infirmly from all sides by the neighbouring molecules. Hence there is no bet force acting on the molecule or there are no unbalanced forces of the molecule. On the oth

    		•