Which range defines fine dispersions in this context?

• A. 0.01-0.1 µm
• B. 10-100 µm
• C. >100 µm
• D. 0.5-10 µm

Answer: (D)

The concept here is particle size in dispersions—the range that still behaves as a fine, easily redispersible suspension without becoming gritty or very unstable. Fine dispersions in pharmaceutics are typically in the micron range, small enough to stay suspended with agitation but large enough to be processed and observed as particles. The range 0.5–10 µm fits this balance: it’s within the micron scale where Brownian motion helps keep particles dispersed, yet not so large that they settle quickly or feel coarse.

Why the other options don’t fit: 0.01–0.1 µm is nanoscale and would be considered a nano- or colloidal dispersion rather than a fine dispersion. Ranges like 10–100 µm or >100 µm are too large for a fine dispersion; such particles tend to sediment rapidly and feel gritty, requiring significant stabilization or viscosity to maintain a suspension.