Question

Identify the diffusible substance for mixtures preparation

• A. Caffeine citrate
• B. Atropine sulphate
• C. Borax
• D. Bismuth carbonate

Hint:

In pharmaceutical formulations, ensure the selected substance is easily diffusible for even distribution in the mixture.

Answer 1

The Correct Option is A

The key distinction in mixture formulation is diffusible vs. indiffusible solids, so we can classify each option accordingly.

1. Caffeine citrate: Correct - classed as a diffusible substance that disperses readily in the mixture vehicle.
2. Atropine sulphate: Not grouped with diffusible bulk solids given its potent, low-dose use.
3. Borax: Used for other formulation roles, not as a diffusible suspension solid.
4. Bismuth carbonate: Classed as indiffusible, requiring a suspending agent to stay dispersed.

So the correct answer is Caffeine citrate.

Answer 2

Another way to work through this is to picture what would happen if each of these substances were simply shaken into a bottle of mixture without any added suspending agent, since that is really what "diffusible" is testing.

1. Caffeine citrate: Being readily dispersible, it would distribute through the liquid without forming a hard, rapidly settling sediment, so a pharmacist would not need to add a special suspending agent just to keep it mixed.
2. Atropine sulphate: Given how small its dose is, dispersion behavior in bulk suspension terms is not really the concern for this drug, and it isn't grouped with the classic bulky diffusible powders used to teach this concept.
3. Borax: Its typical formulation role isn't centered on being shaken into suspension as a bulk solid, so it doesn't fit the diffusible-solid scenario either.
4. Bismuth carbonate: Being a dense, insoluble powder, shaking it into a mixture without a suspending agent would lead to it settling out quickly at the bottom of the bottle, the defining behavior of an indiffusible substance.

Imagining the shake-and-settle scenario for each substance points to the same answer.

Hence, the correct answer is Caffeine citrate.