Distillation in Modern Chemistry Laboratory
>> Saturday, January 22, 2011
In simple terminology, distillation is defined as the method of purifying a liquid by boiling it and condensing its vapors. In other words, any liquid when it is heated and becomes fully boiled, the process of distillation captures and cools the resultant hot vapors, and collect the condensed vapors. This method or process is not a chemical reaction but a unit operation or physical separation. In a modern chemistry laboratory, distillation is a very important requirement to identify and purify the organic compounds.Download Exam Drill of Chemistry for Senior High School Complete with Good Solutions
Boiling Point Determination
The chemistry teaching labs make use of distillation regularly, for two purpose: identification of organic compounds and the purification of organic compounds.
The boiling point of a compound implies the physical features or properties of a compound by which it is distinguished. In a laboratory, distillation is used to purify a compound. This is done by separating the compound from less-volatile or a non-volatile material. There are different compounds in different points in a mixture and the individual components are separated, when there is a careful distillation of the mixture.
This point is actually the temperature at which there is an equality of vapor pressure of the liquid phase of a compound to the external pressure working on the liquid's surface. This outside pressure is usually the atmospheric pressure. The liquid is heated. The vapor pressure of the liquid will increase where there is an increase in the temperature of the liquid. The liquid will boil when the vapor pressure is equal to the atmospheric pressure. It is known that different compounds boil at different temperatures because each compound has its own vapor pressure. It is to be noted that compounds with higher vapor pressures will boil at lower temperatures.
The distillation process of determining a boiling point measures the temperature of the vapors above the liquid and these vapors are the same temperature as the boiling liquid. If the boiling point is used to find a solid compound, it is necessary to compare this with that of the true compound.
Compound Purification Distillation
Simple Distillation: In chemistry laboratory, simple distillation is used. Fractional Distillation: When the boiling points are similar, mixtures of liquids cannot be separated by a single simple distillation. In such cases, fractional distillation is used. It is used to separate the components by vaporization-condensation cycles within a fractionating column and this is repeatedly done.
Vacuum Distillation:This distillation is done at a reduced pressure. In this process, the compound need not be heated to very high temperature for it to boil. This is because, the boiling point of a compound is lower at a lower external pressure. This distillation process is used to distill compounds that have a high point.
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