Question

What are ultrafilters, and how are they prepared?

Answer 1

Ultrafilters are special filter papers with very small pores that can retain colloidal particles while allowing impurities and smaller particles to pass through. They are prepared by treating ordinary filter paper with collodion or gelatin, followed by hardening it in formaldehyde solution. This treatment reduces the pore size, enabling ultrafiltration,a technique useful for purifying colloidal solutions by separating impurities from sols.