What technique allows small molecules to diffuse through semipermeable membranes?

The technique that allows small molecules to diffuse through semipermeable membranes is dialysis. Dialysis is a process in which solvent and small solute molecules move across a semipermeable membrane from a region of higher concentration to a region of lower concentration. This is based on the principle of diffusion, allowing the selective passage of certain substances, such as small molecules, while larger molecules cannot pass through the membrane due to their size.

This technique is widely used in medical treatments, such as artificial kidney machines, where waste products are removed from the blood while retaining larger blood components. Dialysis is specifically designed to facilitate this selective transport, making it suitable for such applications.

In contrast, osmosis refers specifically to the movement of water across a semipermeable membrane rather than other small molecules. Filtration generally involves physical separation based on size without the selective transport characteristic of dialysis. Dilution is a process of reducing concentration through the addition of more solvent and does not involve movement through membranes.