Steam distillation

The steam distillation is a carrier vapor distillation - A separation process, insoluble materials can be separated or purified by the low volatility in the carrier means ( in this case water), such as oils or herbs. The water-insoluble sample is added with hot water in the distillation flask and then steam was passed.

Method

At a carrier vapor distillation, a low boiling component is usually introduced into the solvent, the partial pressure is added to the partial pressure of the higher boiling component, such that the mixture boils more. At the boiling point of the low-boiling component, the particles of the higher boiling are simply swept away. In this way, a reduction in the boiling point can be accomplished. Through this boiling point solvents may decrease gentler distilled or sensitive substances are concentrated gentler (see also vacuum distillation). Water vapor, and the more readily volatile constituents to evaporate and pass the sample gas to the condenser, where it condenses to liquid. If the to-clean material only slightly soluble in water, it separates in the distillate as a second phase and can be separated by decantation and / or extraction. Not all water-insoluble substances are distilled. Substances that are distilled are called steam-volatile. The boiling point of the heterogeneous mixture is always lower than 100 ° C. The reason for this is that the total vapor pressure is not detachable interlocking mixtures from the sum of the partial pressures of the components, regardless of their mole fraction, results. Thus, the total vapor pressure is always higher than the vapor pressure of water, which can boil it at 1013 mbar at 100 ° C. Thus, the boiling temperature must always be below 100 ° C. Therefore, even sensitive natural compounds with very low vapor pressure by this method for distillation.

Application in the analysis ( Kjeldahl method )

For the determination of the nitrogen content is dragged in the analysis by the Kjeldahl method, the ammonia with water vapor from the digested sample, in order then to determine it by titration.

Continuous steam distillation

In the conventional steam distillation, a large amount of steam is required and the actual distillate must first be separated from water. Improve the procedure can through a drip and return flow system: The sample to be distilled, such as parts of plants, located in a round bottom flask with distilled water. In a second, there is an organic solvent which dissolves the desired substance, such as dichloromethane. Both rotary pistons are connected by a glass tube system with each other, whose shape is reminiscent of a trident, with the round bottom flask on the respective outer tip. The central tube is closed at the bottom. From the lower part of the central tube there is a small backflow pipe to the pipe, is connected to that of the round-bottom flask with the solvent. This return flow ends slightly below the height of the water pipe. All three major lines run together at the top and there is a Liebig condenser is placed. The center tube is collected during operation, the distillate is separated into two phases, in the aqueous and the organic. The solvent has a higher density than water, so it collects down and finally arrives in the solvent flask through the reflux again.

After the end of the distillation, the distillate from the rest of the piston means is placed in the solvent flask. Followed by phase separation to a separatory funnel. Then the organic phase is dried over sodium sulfate and filtered. The organic solvent can then be evaporated to obtain the desired natural product mixture.