哪些实验室蒸馏过程将满足我的要求？

Distillation is a common laboratory practice used to isolate and purify liquids on the basis of their volatilities characterized by boiling point differences. Distillation, however, results only in partial isolation of liquids present in mixtures.

在沸点概念以及液体混合物混合物的成分沸点上有清楚起见很重要。液体的沸点是液体的蒸气压等于大气压的温度。在达到沸点上，所有部件的部分压力有助于整体蒸气压。换句话说，液体混合物将具有单一沸点而不是几个沸点。存在于蒸汽中的每个组分的比例将取决于其挥发性。因此，蒸汽将包含在混合物中存在的所有组分，但挥发性组分的比例将最高。

常见的实验室蒸馏程序是：

• 简单蒸馏
• Fractional Distillation
• 蒸汽蒸馏
• Azeotropic Distillation

The different types of distillations are briefly discussed in the article.

简单蒸馏

简单的蒸馏可用于解析液体混合物的液体混合物的组分（25-30 ^ 0C \）。产生的蒸气通过冷凝器纳入收集容器，在那里它是液化的。液化成分不会纯度为100％，但将具有更高比例的挥发性组分。当蒸汽的温度开始上升到所需组分的沸点时，应停止蒸馏。对于具有更近沸点的液体，收集的液体可以进行一个或多个蒸馏阶段。

Fractional Distillation

Fractional distillation is essentially same as simple distillation and is useful when the boiling points of constituent liquids lie within a narrower range. The distillation process is repetitive but takes place inside the condenser tube .It affords saving of time over the repetitive simple distillations and is more efficient than multiple steps in simple distillations. The same re-distillation is affected repetitively inside the fractionating column.

在冷凝器管内的环，板或封装上上升的蒸汽回忆。它被升高的热蒸汽升压。每个汽化 - 冷凝循环用挥发性组分富集蒸气。

蒸汽蒸馏

蒸汽蒸馏should be preferred over fractional distillation for separation of heat sensitive compounds which can degrade on the uncontrolled heating of the solid supports inside the fractionating column. Steam on the other hand promotes the same purpose in a more controlled manner. However, the collected distillate is in two layers, namely, an oily layer and water layer which will require further steps to isolate the pure compound.

Vacuum Distillation

具有非常高沸点的化合物需要蒸馏的较高温度才能有效。如果压缩管内的压力降低而不是提高温度，则可以保持化合物的稳定性。降低温度降低了较高沸点组分的沸点。真空蒸馏通常通过使用旋转蒸发器来进行。

Azeotropic Distillation

在液体混合物的分子水平上的相互作用can result in alteration of the boiling point of the mixture. The mixture boils at a temperature which is lower or higher than the boiling points of the constituent pure compounds. On reaching the boiling point a constant composition vapours results which distil over without separation of the original components. A common example is ethanol and water which forms an azeotrope of 96.5% at \(78.1^0 C\) .The azeotropic composition can be altered if further purification is required. A drying agent, such as potassium carbonate, can be added to remove the residual water and distil the ethanol to higher purity levels.

The same laboratory scale preparations form the basis of large scale industrial distillation processes which provide separations of tons of liquid fractions on daily basis. Such industrial separations are common in petroleum, petrochemicals and organic chemical industries.