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

Each type of oil has its own standard oil:water:gum ratio for the primary emulsion, so we just need to identify mineral oil's specific ratio.

1. 4:2:1: This is the ratio for fixed (vegetable) oils, not mineral oil.
2. 2:2:1: This is the ratio for volatile oils, not mineral oil.
3. 3:2:1: Correct - this is the standard ratio for mineral oil (liquid paraffin).
4. 1:2:4: This does not correspond to any of the standard oil-type ratios.

So the correct answer is 3:2:1.

Answer 2

A different way to arrive at the same answer is to notice the pattern across the three recognized oil categories rather than memorizing mineral oil's ratio directly: as an oil becomes harder to emulsify it needs less oil relative to gum, and mineral oil sits in the middle of this spectrum between fixed oils and volatile oils.

1. Fixed oils (most easily emulsified): Take the highest oil:gum ratio among the three categories, which is 4:2:1, not applicable here since mineral oil is not a fixed oil.
2. Volatile oils (hardest to emulsify with gum, being thin and mobile): Take the lowest oil:gum ratio, which is 2:2:1, also not applicable, since mineral oil isn't a volatile oil.
3. Mineral oil (intermediate difficulty): Sitting between these two extremes, it takes the middle ratio of the three, which is 3:2:1, matching its intermediate position in the spectrum.
4. 1:2:4: This ratio doesn't fit anywhere on this fixed-to-volatile spectrum at all, since it would mean using far more gum than oil, which none of the three recognized oil categories require.

Reasoning from the relative position in the oil spectrum gives the same ratio.

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