Simple and Fractional Distillation

Distillation is a technique frequently used to separate and purify a liquid component from a mixture. Simply stated, distillation involves heating a liquid mixture to its boiling point, where liquid is rapidly converted to vapor. The vapors, richer in the more volatile component, are then condensed into a separate container. When the components in the mixture have sufficiently different vapor pressures (or boiling points), they can be separated by distillation. 

The purpose of this experiment is to illustrate the use of distillation for separating a mixture of two volatile liquids with different boiling points. Each mixture, which will be issued as an unknown, will consist of two liquids from the following table. 

The liquids in the mixture will be separated by two distillation techniques simple and fractional distillation. The results of these two methods will be compared by analyzing the composition of the distillate (the distilled liquid) using gas chromatography. You will also construct a graph of the distillation temperature versus the total volume of distillate collected. This graph will allow you to determine the approximate boiling points of the two liquids and to make a graphical comparison of the two distillation methods. 

Experiment 7A is designed to be performed with semimicroscale glassware using a conventional distillation apparatus. A microscale alternative with a Hickman head is given in Experiment 7B however, the scale is the same in both cases, and the experiment can be performed more easily wifh the semimicroscale glassware. 

Many flammable solvents are used in this experiment therefore, do not use any flames in the laboratory. 

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Setups for simple and fractional distillation at atmospheric pressure are shown (Fig. A3.13). A 30-cm Vigreux column (Fig. A3.13b) is convenient if the components boil at least 50° apart at atmospheric pressure. For better separation, a column packed with glass helices is suitable. All columns employed in fractional distillation should be wrapped or jacketed to minimize heat loss. 

Simple and fractional distillations will be discussed in this chapter, but no experiments are provided because most students will have done experiments of this type previously. Such a discussion will permit the major areas of distillation to be put in proper perspective. 

Pressure distillation Simple and fractional distillation Flash distillation Thin-fUm distillation Thin-film distillation Molecular distillation... 

EXPERIMENT 7A Simple and Fractional Distillation (Semimicroscale Procedure)... 

Record the data for the distillation temperature as a function of the volume of distillate. Construct a graph for these data (see "Analysis" in Experiment 7A). Compare the graphs for simple and fractional distillations of the same mixture. Which distillation resulted in a better separation Explain. Report the approximate boiling points for the two compounds in your mixture and identify the compounds. 

Apparatus A 25-mL and two 10-mL round-bottom flasks, drying tube, ice-water bath, apparatus for simple and fractional distillation, magnetic stirring, and flameless heating. 

What is the difference between simple distillation and fractional distillation ... 

Vacuum or reduced-pressure distillation used for separating liquids boiling above 200 °C, when decomposition may occur at the high temperature. The effect of distilling at reduced pressure is to lower the boiling point of a liquid. This technique can be applied to both simple distillation and fractional distillation. 

Uses of Oieochemicais Based on Palm Oil and Palm Kernel Oil. (a) Fatty Acids. The most common method for the production of fatty acids adopted by the oieochemicais industry is high-temperature and high-pressure fat splitting. The fatty acid mixture produced is separated into broad cuts or pure fatty acids by simple or fractional distillations. Tables 50 and 51 list examples of fatty acids derived from palm products. The exact specifications of the various fatty acids produced vary slightly depending on the exact raw materials and process used. The specifications could also change due to continuous upgrading of processes. 

Lemongrass oil contains a number of substances simple or fractional distillation would not be a practical method for obtaining pure citral. And because it boils at 229°C, it has a tendency to polymerize, oxidize, and... 

Hey Not so fast It s not that simple. You see, for some reason, the world s camphor trade likes to take that crude camphor oil and fractionally distill it into its component parts of which there are three ... 

Distillation [4]. Distillation is a technique used for separation of components in a single liquid stream. This separation is based on the different boiling points of the components. At the industrial level, one of the best known processes is the production of gasoline. Different types of distillation include, for example, simple distillation and fractional distillation. A mixture of... 

The principal commercial source of rubidium is accumulated stocks of a mixed carbonate produced as a byproduct in the extraction of lithium salts from lepidohte. Primarily a potassium carbonate, the byproduct also contains ca. 23 wt.% rubidium and 3 wt.% cesium carbonates. The primary difficulty associated with the production of either pure rubidium or pure cesium is that these two elements are always found together in nature and also are mixed with other alkali metals because these elements have very close ionic radii, their chemical separation encounters numerous issues. Before the development of procedures based on thermochemical reduction and fractional distillation, the elements were purified in the salt form through laborious fractional crystallization techniques. Once pure salts have been prepared by precipitation methods, it is a relatively simple task to convert them to the free metal. This is ordinarily accomplished by metallothermic reduction with calcium metal in a high-temperature vacuum system in which the highly volatile alkali metal is distilled from the solid reaction mixture. Today, direct reduction of the mixed carbonates from lepidolite purification, followed by fractional distillation, is perhaps the most important of the commercial methods for producing rubidium. The mixed carbonate is treated with excess sodium at ca. 650 C, and much of the rubidium and cesium passes into the metal phase. The resulting crude alloy is vacuum distilled to form a second alloy considerably richer in rubidium and cesium. This product is then refined by fractional distillation in a tower to produce elemental rubidium more than 99.5 wt.% pure. 

For either the simple or fractional distillation, place a boiling stone into the 10-mL round-bottom flask. Also add 8.0 mL of the unknown mixture (measured with a 10-mL graduated cylinder) to the flask. Use a hot plate and an aluminum block for heating. 

The simple, vacuum, and fractional distillations described in Techniques 14,15, and 16 are applicable to completely soluble (miscible) mixtures only. When liquids are not mutually soluble (immiscible), they can also be distilled, but with a somewhat different result. A mixture of immiscible liquids will boil at a lower temperature than the boiling points of any of the separate components as pure compounds. When steam is used to provide one of the immiscible phases, the process is called steam distillation. The advantage of this technique is that the desired material distills at a temperature below 100°C. Thus, if unstable or very high-boiling substances are to be removed from a mixture, decomposition is avoided. Because all gases mix, the two substances can mix in the vapor and codistill. Once the distillate is cooled, the desired component, which is not miscible, separates from the water. Steam distillation is used widely in isolating liquids from natural sources. It is also used in removing a reaction product from a tarry reaction mixture. 

Two miscible liquids Distillation (simple and fractional) Boiling point Ethanol (alcohol) and water... 

If the ether is a simple one (R — R ), the identification of the resulting alkyl iodide presents no difficulties. If, however, it is a mixed aliphatic ether, the separation of the two alkyl iodides by fractional distillation is generally difficult unless R and R differ considerably in molecular weight and sufficient material is available. 

Assemble the simple fractional distillation apparatus shown in Fig. II, 16, 1 the round-bottomed flask should have a capacity of 200 or 250 ml. and the conical flask 100 ml. (Alternatively, a long all-glass... 

In order to obtain pure aromatics, cmde reformate is extracted to separate the aromatics from unreacted paraffins and cyclop araftins. The aromatics are, in turn, separated by simple fractional distillation to yield high purity benzene, toluene, xylenes, and aromatics. 

One of the most widely applicable and most commonly used methods of purification of liquids or low melting solids (especially of organic chemicals) is fractional distillation at atmospheric, or some lower, pressure. Almost without exception, this method can be assumed to be suitable for all organic liquids and most of the low-melting organic solids. For this reason it has been possible in Chapter 4 to omit many procedures for purification of organic chemicals when only a simple fractional distillation is involved - the suitability of such a procedure is implied from the boiling point. 

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