Simple distillation fractions

Apparatus A 25- and a 50-mL round-bottom flask, drying tube, Claisen adapter, separatory funnel, gas trap, apparatus for simple distillation, fractional distillation, magnetic stirring, and flameless heating. 

Benzene is a natural component of petroleum, but the amount of benzene present ia most cmde oils is small, often less than 1.0% by weight (34). Therefore the recovery of benzene from cmde oil is uneconomical and was not attempted on a commercial scale until 1941. To add further compHcations, benzene cannot be separated from cmde oil by simple distillation because of azeotrope formation with various other hydrocarbons. Recovery is more economical if the petroleum fraction is subjected to a thermal or catalytic process that iacreases the concentration of benzene. 

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. 

Fig. A3.13. Setups for atmospheric pressure distillation (a) for simple distillation (b) Vigreux column for fractional distillation.

The volatilities of both zirconium tetrachloride and hafnium tetrachloride are very similar to each other at normal operating temperatures, and their separation by a simple distillation or fractional distillation operation is not viable. However, when the mixed chloride vapor is contacted with an eutectic molten salt mixture of aluminum chloride and potassium chloride, zirconium chloride is preferentially absorbed. The vapor pressure difference between zirconium and hafnium tetrachlorides is greatly enhanced over the molten... 

A 1-1. steel bomb is charged with 200 g. (1.51 moles) of dicyclo-pentadiene (Note 1). The bomb is flushed with ethylene (Note 2) and then filled while shaking to an initial pressure of 800-900 p.s.i. at 25°. Shaking is continued as the bomb is slowly heated (Note 3) to 190-200° and maintained at this temperature for 7 hours (Note 4). At the end of this period, the reaction vessel is cooled and vented, and the crude product is transferred into a simple distillation apparatus (Note 5). A fraction boiling between 93° and 100° is collected, yield 162-202 g. (57-71%, based on dicyclopentadiene) (Note 6). The norbornylene may be redistilled with negligible losses to give a final product, b.p. 94-97°/740 mm., m.p. 44-44.5° (sealed capillary). 

It is desired to separate a binary mixture by simple distillation. If the feed mixture has a composition of 0.5 mole fraction, calculate the fraction which it is necessary to vaporise in order to obtain ... 

For separation of liquids, soluble in each other, that boil less than 25 °C from each other, use fractional distillation. This is like simple distillation with the changes shown (Fig. 80). 

Why does one simple distillation remove most of the dissolved hardness minerals from tap water, while many distillations (or a fractionating column) are required to separate a mixture of two liquids ... 

The difference in vapor pressure and boding point of water and dissolved hardness minerals is substantial, such that one simple distillation will result in significant purification. In the case of two liquids, however, these differences are much narrower, such that many distillations or a fractionating column is required. 

Two liquids in a mixture typically have a significant vapor pressure and similar boiling points. Thus, a clean separation does not occur with only a simple distillation. A fractional distillation is usually required. 

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

A simple distillation B fractional distillation C evaporation D chromatography E filtration F diffusion... 

Should the temperature rise steadily, instead of remaining virtually constant, it is then clear that this simple distillation procedure is unsuitable for the purification of the sample and some form of fractional distillation (Section 2.26) will have to be used. 

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