Question

Dose of formalin for preserving 100ml of milk sample is:

• A. 1 ml
• B. 5 ml
• C. 0.4 ml
• D. 0.1 ml

Hint:

Remember: Formalin is added at a rate of \(0.1\%\) of the sample volume.
For a \(100\text{ ml}\) milk sample, \(0.1\%\) corresponds exactly to \(0.1\text{ ml}\) (or about 2 drops).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Chemical preservatives are added to milk samples to prevent microbial growth and chemical changes during storage or transport prior to laboratory analysis.

Step 3: Detailed Explanation:
1. Formalin (a \(36\%\) to \(40\%\) solution of formaldehyde) is a widely used liquid chemical preservative for milk samples meant for chemical testing (but not for microbiological analysis, as it kills the bacteria).
2. The standard recommended dose of formalin to preserve milk is \(0.1\text{ ml}\) per \(100\text{ ml}\) of milk sample.
3. This concentration is sufficient to keep the milk sample stable for several days at room temperature without significantly altering the results of routine chemical tests (such as fat and SNF determination).

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