Question

Detection of pond water in milk using diphenylamine is based on the presence of ......... in pond water:

• A. Sulphates
• B. Chlorides
• C. Nitrates
• D. Citrates

Hint:

Diphenylamine = Nitrate detection test.
Since municipal tap water contains very low nitrates compared to pond or well water, a positive diphenylamine test is a strong indicator of pond/groundwater dilution.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Adulteration of milk with water is common, but identifying the source of water can help confirm intentional adulteration with unsanitary water sources like ponds, canals, or wells.

Step 3: Detailed Explanation:
1. Natural milk contains virtually no nitrates.
2. Pond water, well water, and canal water often contain significant amounts of nitrates originating from agricultural fertilizers, organic waste, and surface runoff.
3. The diphenylamine test is used to detect the presence of nitrates in milk.
4. When diphenylamine reagent is added to milk adulterated with pond water, the nitrates react to form a distinct blue-colored complex.
5. Thus, the test relies on the presence of nitrates in the added water.

Step 4: Final Answer
The correct option is (C).