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 : Colligative property problem Which is

    Which is not a colligative property: (a) Refractive index (b) Lowering of vapour pressure (c) Depression of freezing point (d) Elevation of boiling point    

  • Q : Why medications include the hcl Why do

    Why do various medications include the hcl? Describe briefly?

  • Q : Which is largest planet in our solar

    which is largest planet in our solar system

  • Q : What is electrolysis? Explain with

    Passage of a current through a solution can produce an electrolysis reaction.Much additional information on the properties of the ions in an aqueous solution can be obtained from studies of the passage of a direct current (dc) through a cell containing a s

  • Q : Define thermal energy The thermal part

    The thermal part of the internal energy and the enthalpy of an ideal gas can be given a molecular level explanation. All the earlier development of internal energy and enthalpy has been "thermodynamic". We have made no use o

  • Q : Inorganic Chemistry Inorganic

    Inorganic Chemistry:In the year 1869, Russian Chemist Dmitry Mendeleyev forms the periodic table of the element. Since Newlands did before him in the year 1863, Mendeleyev categorizes the el

  • 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

  • Q : Volume hydrogen peroxide Choose the

    Choose the right answer from following. The normality of 10 lit. volume hydrogen peroxide is: (a) 0.176 (b) 3.52 (c) 1.78 (d) 0.88 (e)17.8

  • Q : Explain Rotational Vibrational Spectra

    The infrared spectrum of gas samples shows the effect of rotational-energy changes along with the vibrational energy change.As we know from the interpretations given to thermodynamic properties of gases, gas molecules are simultaneously rotating and vibrating. It follows that an absor

  • Q : Question related to molarity Help me to

    Help me to go through this problem. Molarity of a solution containing 1g NaOH in 250ml of solution: (a) 0.1M (b) 1M (c) 0.01M (d) 0.001M

©TutorsGlobe All rights reserved 2022-2023.