Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A): In RM value determination, glycerol is used as a medium for saponification of ghee with sodium hydroxide.
Reason (R): Boiling point of glycerol is high and hence it is not distilled off along with steam volatile constituents of the medium.
In light of the above statements, choose the correct answer from the options given below.

• A. Both (A) and (R) are true and (R) is the correct explanation of (A)
• B. Both (A) and (R) are true but (R) is NOT the correct explanation of (A)
• C. (A) is true but (R) is false
• D. (A) is false but (R) is true

Hint:

In RM and Polenske value determinations:
- Glycerol provides a high-temperature, foam-free medium for complete saponification.
- Its high boiling point (290°C) ensures it remains in the flask during steam distillation of the volatile fatty acids.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The Reichert-Meissl (RM) value is a chemical index used to evaluate the purity of ghee and detect adulteration with foreign fats.
It measures the quantity of water-soluble, steam-volatile fatty acids (primarily butyric and caproic acids) present in 5 g of fat.
The first step of the RM value determination is the saponification of the fat sample to break down the triglycerides into glycerol and sodium soaps.

Step 2: Detailed Explanation:
Let us analyze the role of glycerol in this method:
-Assertion (A):
To hydrolyze the fat, the sample is heated with concentrated sodium hydroxide.
Using water as a solvent is difficult because it evaporates quickly and causes severe foaming, which can lead to incomplete saponification.
Therefore, glycerol is used as the reaction medium.
Glycerol is miscible with both fat and sodium hydroxide, allowing for a homogeneous, anhydrous saponification reaction at high temperatures without foaming.
Thus, Assertion (A) is true.
-Reason (R):
Glycerol has a high boiling point of approximately 290°C.
During the subsequent step of the test, the saponified mixture is acidified, and steam is passed through it to distill over the liberated volatile fatty acids.
Because of its high boiling point, glycerol remains stable in the flask and does not distill over with the steam.
This prevents glycerol from contaminating the distillate and interfering with the subsequent titration of the volatile acids.
Thus, Reason (R) is true and provides the correct scientific explanation for why glycerol is used as the saponification medium.

Step 3: Final Answer:
Both (A) and (R) are true, and (R) is the correct explanation of (A), which corresponds to Option (A).