What technique is used to separate a soluble solid from a liquid?

Crystallization is the technique used to separate a soluble solid from a liquid. This process involves forming solid crystals from a solution as it cools or as the solvent evaporates. When a solution containing a dissolved solid is heated, the solubility of the solid increases, allowing it to dissolve in the liquid. As the solution cools, the solubility decreases, leading the dissolved solid to come out of solution and crystallize. This method is especially useful for purifying the solid, as the crystals can often be collected and the impurities will remain dissolved in the liquid.

Filtration is a method used for separating solid particles from a liquid, but in the case of a soluble solid, the solid is dissolved, and therefore filtration would not be effective. Condensation refers to the transition from gas to liquid, which is not relevant to separating soluble solids from liquids. Precipitation is a process that involves forming a solid (precipitate) from a solution, typically by adding a reagent, but it is more about the reaction resulting in an insoluble compound rather than separating a soluble solid from a liquid. Thus, crystallization is the most appropriate technique for this separation process.