Question

Which is the correct proportion of oil, water, gum for preparation of primary emulsion using mineral oil

• A. 4:2:1
• B. 2:2:1
• C. 3:2:1
• D. 1:2:4

Hint:

For primary emulsions, a ratio of 3 parts oil, 2 parts water, and 1 part gum is commonly used.

Answer 1

The Correct Option is C

Step 1: Understanding the primary emulsion composition.
Primary emulsions are prepared using a mixture of oil, water, and gum. The gum acts as an emulsifying agent that stabilizes the emulsion. The proportions vary depending on the type of emulsion. For primary emulsions using mineral oil, the common ratio of oil, water, and gum is typically 3:2:1.
Step 2: Analyzing the options.
(A) 4:2:1: This ratio is not typical for a primary emulsion.
(B) 2:2:1: This is not the standard ratio for emulsions.
(C) 3:2:1: Correct — This is the most commonly used proportion for preparing primary emulsions, with the right balance of oil, water, and gum.
(D) 1:2:4: This is an incorrect ratio for primary emulsions.
Step 3: Conclusion.
The correct answer is (C) 3:2:1 as it is the standard ratio for the preparation of primary emulsions using mineral oil.

Answer 2

The classic ratios for preparing a primary emulsion by the gum (dry gum/English) method vary depending on the type of oil being emulsified, since different oils require different amounts of gum relative to water. Matching mineral oil to its recognized ratio among the options settles the question.

1. 4:2:1: This ratio is the one conventionally used for fixed (vegetable) oils, such as olive oil or castor oil, which need proportionally more oil relative to gum because they are easier to emulsify, not the ratio for mineral oil.
2. 2:2:1: This lower oil-to-gum ratio is the one conventionally used for volatile oils (such as essential oils), which are thinner and require relatively more gum and water relative to oil, again not the mineral oil ratio.
3. 3:2:1: Mineral oil (liquid paraffin) sits between fixed oils and volatile oils in terms of how much gum it needs to emulsify well, and the standard ratio used for it in pharmacy practice is 3 parts oil to 2 parts water to 1 part gum.
4. 1:2:4: This ratio reverses the typical proportions (far more gum than oil), which does not correspond to any of the standard primary-emulsion ratios used for fixed, volatile, or mineral oils.

Matching mineral oil to its recognized position among the standard ratios points to only one option.

Therefore, the correct answer is 3:2:1.