Sublimation is a unit operation that could receive much greater attention in the future as a purification method. From a frequent batch process used for simple separation of a desired volatile constituent from a nonvolatile impurity, sublimation can progress to continuous, multistage methods for fractionating materials of differing volatility on a large industrial scale. This will be particularly important for materials that decompose at temperatures below the melting point and that have low solubilities in common solvents. More experimental information, particularly as regards the factors influencing the condensation of solids from the vapor, would be of value in design of equipment.