升华提纯Sublimation apparatus

物质能否升华取决于其三相点：当三相点压力高于或接近操作压力时，加热固体会直接变成气体。碘、萘、樟脑、干冰、咖啡因、苯甲酸等在常压或减压下易升华。减压可降低升华温度，使更多物质适用。升华提纯可得到很纯的晶体，但只适用于有足够蒸气压且杂质不挥发的情况。

Whether a substance sublimes depends on its triple point: when the triple-point pressure is above or near the working pressure, a heated solid turns directly into gas. Iodine, naphthalene, camphor, dry ice, caffeine and benzoic acid sublime readily at atmospheric or reduced pressure, and vacuum lowers the sublimation temperature so more substances qualify. Sublimation gives very pure crystals but works only when the compound has enough vapour pressure and the impurities are non-volatile.

最简单的方法是把样品放在蒸发皿中，上面盖一张扎有小孔的滤纸和一个倒置的漏斗，加热后升华物在漏斗内壁凝结。实验室常用带“冷指”（通冷却水的指形冷凝管）的升华管，可在减压下进行。高真空梯度升华用于纯化 OLED 有机半导体材料，纯度可达 99.9% 以上。

The simplest set-up puts the sample in an evaporating dish under a perforated filter paper and an inverted funnel; on heating, the sublimate collects inside the funnel. Laboratories usually use a sublimation tube with a water-cooled 'cold finger', which can run under vacuum. High-vacuum gradient sublimation purifies organic semiconductors for OLEDs to above 99.9%.

升华用于提纯碘、萘、樟脑和二茂铁，从茶叶中升华提取咖啡因，制备高纯有机光电材料，以及冷冻干燥（冰在真空下升华）保存食品、药品和生物样品。

Sublimation purifies iodine, naphthalene, camphor and ferrocene, extracts caffeine from tea, prepares high-purity organic optoelectronic materials, and in freeze-drying, where ice sublimes under vacuum, preserves foods, drugs and biological samples.