Question

Organic Chemistry Laboratory Techniques

What is a Steam Distillation and Simple Distillation? Explain the process for both techniques

Answer 1

Steam distillation is a separation process used to purify or isolate temperature sensitive materials, like natural aromatic compounds. Steam or water is added to the distillation apparatus, lowering the boiling points of the compounds. The goal is to heat and separate the components at temperatures below their decomposition point. When a mixture of two immiscible liquids (e.g., water and organics) is heated and agitated, the surface of each liquid exerts its own vapor pressure as though the other component of the mixture was absent. Thus, the vapor pressure of the system increases as function of temperature beyond what it would be if only one of the components was present. When the sum of the vapor pressures exceeds atmospheric pressure, boiling begins. Because the temperature of boiling is reduced, damage to heat- sensitive components is minimized Steam distillation is useful for the purification of organic compounds, although vacuum distillation is more common. When organics are distilled, the vapor is condensed. Because water and organics tend to be immiscible, the resulting liquid generally consists of two phases: water and the organic distillate. Decantation or partitioning may be used to separate the two layers to obtain the purified organic material. Steam distillation is the preferred method used to isolate essential oils. It is also used for steam stripping" in petroleum refineries and to separate commercially important organi compounds, such as fatty acids. Simple distillation is a form of distillation, two liquids that can be mixed that have drastically different boiling points. Heating up the mixture allows the one with the much lower boiling point to evaporate off and then you can cool it down and collect it. Steam distillation is used for water and typically a chemical compound that doesn't mix with water, because if they don't mix then the mixture will always boil at or below the boiling point of water. You use steam distillation to distill compounds that would otherwise burn at high temperatures. It's only somewhat effective because you're going to get water contamination whereas with simple distillation you can get a pretty pure product. For example, water can be separated from salty water by simple distillation. This method works because the water evaporates from the solution, but is then cooled and condensed into a separate container. The salt does not evaporate and so it stays behind