Preparation and stability studies of emulsions

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The physical stability of the emulsion is important to keep the dispersion intact. A stable emulsion is one in which the dispersed globules retain their character and remain uniformly distributed throughout b the continuous phase. The unstable condition in emulsion are: creaming, coalescence ,cracking or breaking and phase inversion.

The physical stability of an emulsion can be assessed by an examination of degree of creaming or coalescence occurring over a period of time. The ratio of volume of creamed part of an emulsion to the total volume is the required indicator. The globule size analysis can be used to assess stability.1,2

Aim: To assess the physical stability of benzyl benzoate location (an emulsion for external use)

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Materials and apparatus:     Benzyl Benzoate,

Tri-Ethanol Amine,

Oleic Acid,


Beaker/Conical Flask,


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Preparation of emulsion (benzyl benjoate loation):-(at least 3 emulsions to be prepared using the same formula and in the laboratory, data

From other students can be used)

Formula for benzyl benjoate loation:-

Benzyl benzoate -25ml

Triethanol amine-0.5 g.

Oleic acid -2 g.

water -75 ml.

To make around 100 ml (the density of the triethanol amine is 1.12 g/ml and that of oleic acid is 0.895 gm/ml.this can be used to convert weight into volume) Triethanol amine is mixed with oleic acid .benzyl benzoate is added and mixed.nThe mixture is transferred to abottle of around 200 ml capacity (double the volume required to prepare) 25 ml water is added and the mixture is thoroughly shaken. The remaining 50 ml water is added and shaken thoroughly.3

Extent of creaming

The prepared emulsion is trafered to a 100 ml measuring cylinder . The emulsion is left undisturbed in the cylinder and the volume of cream developed is noted over time from 0 to 2 hour at a frequency of every 30 minutes. The graph is plotted taking of crimming in y axis and time in x axis

Observation and calculation

Number of observation

Time in minutes

Volume of cream in ml.

Degree of creaming (volume of cream+total volume of emulsion )











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The creaming instability of emulsion is obserbed in the following order …

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  1. More HN, Hajare AA. Practical Physical Pharmacy. Career Publications. 2010: 205-207.
  2. Gaud RS, Gupta GD. Practical Physical Pharmacy. CBS Publisher and Distributors. 85-86.
  3. Mohanta GP. Physical Pharmacy Practical Text, Pharma Book Syndicate. 2006: 75-76.