Small-scale sublimation apparatus

Sublimation.—This is a valuable means for the purification of many organic substances and is admirably adapted for small scale work since losses are generally small. Sublimation may be carried out either at atmospheric pressure or under reduced pressure. The apparatus shown in Fig. XII, 2, 20 is simple and effective the sublimate is collected on the cold finger condenser. 

Sublimation is a technique that is much easier to carry out on a small sccile than on a large one. It would be unusual for a research chemist to sublime more than about 10 g of material, because the sublimate tends to fall back to the bottom of the apparatus. In an apparatus such as that illustrated in Fig. 14(a), the solid to be sublimed is placed in the lower flask and connected via a lubricant-free rubber 0-ring to the condenser, which in turn is connected to a vacuum pump. The lower flask is immersed in an oil bath at the appropriate temperature and the product sublimed and condensed onto the cool walls of the condenser. The parts of the apparatus are gently sepcu ated and the condenser inverted the vacuum connection serves as a convenient funnel for product removal. For large-scale work the sublimator of Fig. 14(b) is used. The inner well is filled with a coolant (ice or dry ice). The sublimate clings to this cool surface, from which it can be removed by scraping and dissolving in an appropriate solvent. 

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