All About Steam Distillation

In the separation process of steam distillation, water is combined with other volatile and nonvolatile components and then distilled at high temperatures. A condenser is used to cool and return the volatiles back to their liquid or solid states. The non-volatile residues are left behind in the boiling container because they are carried by the steam from the boiling water.

If the volatiles are liquids that are not miscible in water, they will spontaneously form a distinct process after condensation, which will allow them to be separated by decantation or with a separatory funnel after the condensation process. A Clevenger apparatus can be used to return the condensed water to the boiling flask while the distillation process is taking place in this case, if necessary. As an alternative, the condensed mixture can be processed using fractional distillation or another type of separation procedure.

When the boiling point of the substance to be extracted is greater than the boiling point of water and the starting material cannot be warmed to that temperature due to breakdown or other undesirable reactions, steam distillation can be used to extract the desired ingredient. It may also be beneficial when the amount of the desired substance is insignificant when compared to the amount of non-volatile residues present in the sample. It is frequently employed in the extraction of volatile essential oils from plant material.

Using the most basic method, water distillation (also known as hydrodistillation), the water is combined with the starting material in a boiling container. If you are using direct steam distillation, you will be suspending your starting material above the water in the boiling flask, which is supported by a metal mesh or perforated screen. Steam from a boiler is forced to pass through the starting material in a separate container, which is known as dry steam distillation. The latter variant allows for the steam to be heated above the boiling point of water (thus resulting in superheated steam), resulting in more efficient extraction of the liquid.

Principal of Steam Distillation

Every substance, even at temperature below its boiling point, has some vapour pressure, which means that it may theoretically be distilled at any temperature by gathering and condensing the vapours released by the substance during the process. Normal distillation below the boiling point is not feasible in practice because a layer of air densely packed with vapour will accumulate on top of the liquid, preventing the liquid from reaching its boiling point. It will come to an abrupt halt as soon as the partial pressure of water vapour in that layer equals the vapour pressure, which will occur in about a second. If the vapour is to reach the condenser, it will have to do so through diffusion, which is an extremely slow process.

However, in steam distillation, that positive flow is provided by the steam produced by boiling water, rather than by heating the substances of interest to boiling temperatures. In addition, the steam carries the vapours produced by the latter.

It is not necessary for the substance of interest to be miscible with water or soluble in it. It is sufficient that it has a significant vapour pressure at the temperature of the steam to qualify.

If the water reacts with the substances of interest to form an azeotrope, the boiling point of the mixture may be lower than the boiling point of water, which is undesirable. For example, bromobenzene boils at 156 degrees Celsius (at normal atmospheric pressure), but it boils at 95 degrees Celsius when mixed with water. Steam distillation, on the other hand, is not dependent on the formation of an azeotrope in order to function. 

Application of Steam Distillation

Steam distillation is frequently used in the extraction of essential oils, which are then used in the production of perfumes, among other things. Through the use of this method, steam is passed through the plant material that contains the desired oil. This method is used in the production of eucalyptus oil, camphor oil, and orange oil on a large industrial scale.

Steam distillation is also occasionally employed in chemical laboratories as one of the many different methods of substance separation.

Also useful for extracting and separating fatty acids from mixtures, steam distillation is used to treat crude products such as tall oils in order to extract and separate fatty acids and other commercially valuable organic compounds.

Conclusion

In the separation process of steam distillation, temperature-sensitive materials such as natural aromatic compounds are purified or isolated from the rest of the mixture. In the separation process of steam distillation, water is combined with other volatile and nonvolatile components and then distilled at high temperatures.

Using the most basic method, water distillation (also known as hydrodistillation), the water is combined with the starting material in a boiling container.

In steam distillation, that positive flow is provided by the steam produced by boiling water, rather than by heating the substances of interest to boiling temperatures. 

Steam distillation is frequently used in the extraction of essential oils, which are then used in the production of perfumes, among other things. Steam distillation is also occasionally employed in chemical laboratories as one of the many different methods of substance separation.