Procedure
Follow these steps To study the saponification value of an oil/fat by titrimetric method.
Preparation of Reaction Mixture:
- A known concentration of the ester (e.g., ethyl acetate) is mixed with excess water and a strong acid catalyst, such as hydrochloric acid (HCl).
- Sampling at Intervals: The reaction mixture is allowed to proceed, and small aliquots are taken at regular time intervals. These aliquots are quenched by adding a known amount of sodium hydroxide (NaOH) to neutralize the acid catalyst.
-
Titration:
The remaining acid is titrated against a standard solution of NaOH to determine the concentration of
unreacted acid at each time point.
-
Calculation:
The titration data are used to calculate the concentration of ester at different time intervals. The rate
constant, k, is determined from the slope of the plot of the natural logarithm of the concentration of the
ester versus time.
Safety Precautions:
1. Clamp the burette perfectly in the vertically, so that it is easy to
read the scale properly.
2. Before use rinse the burette thoroughly, while filling the burette no air bubble should be present in
the
burette and dispense off working solution from the burette.
3. Remove funnel after filling burette up to mark zero. Read the lower meniscus of the burette.
4. Add same number of drops (vol.) of indicator in each titration.
5. To get better visibility of color change at the end point use filter paper below the conical
flask.
6. During titration conical flask should be stirred continuously and correctly observe the end
point.
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