Expt 03 - Simple and Fractional Distillations

Expt 03 - Simple and Fractional Distillations - EXPERIMENT...

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Figure 1 : The apparatus for a simple distillation. EXPERIMENT THREE Distillations Part One - Simple Distillations Discussion This experiment is a simple distillation of a mixture of cyclohexane and toluene. We will first describe the general steps used in any simple distillation, then mention some specific features of this experiment. Steps in a Simple Distillation The apparatus for a simple distillation is shown in the figure above. Study this figure carefully, noting the placement and clamping of the distillation flask, the distillation head, and the condenser. Note that water flows into the bottom of the condenser's cooling jacket and out the top. If the water inlet were at the top, the condenser would not fill. Also, note the placement of
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the thermometer bulb, just below the level of the side arm of the distillation head. If the bulb were placed higher than this position, it would not be in the vapor path and consequently would show an erroneously low reading for the boiling point. >>>SAFETY NOTE : Distillation of noxious or toxic substances should always be carried out in a fume hood. Special precautions should also be taken with distillations of highly flammable substances, such as most solvents. Never use a burner in these cases, and avoid allowing an excess of uncondensed vapors to flow into the room. 1) The distillation flask . Use only a round-bottom flask, never an Erlenmeyer flask, for distillation. The flask should be large enough that the material to be distilled fills 1/3 of its volume. If the flask is overly large, a substantial amount of distillate will be lost as vapor filling the flask at the end of the distillation. If the flask is too small, boiling material may foam, splash, or boil up into the distillation head, thus ruining the separation. Grease the ground-glass joint of the flask lightly, then securely clamp the flask to a ring stand or rack. Before adding liquid, support the bottom of the flask with an iron ring and a heating mantle. The heating mantle should fit snugly around the flask. Introduce the liquid into the distillation flask, using a funnel with a stem to prevent the liquid from contaminating the ground-glass joint. Finally, add three or four boiling chips. (CAUTION: Never add boiling chips to a hot liquid!) 2) The distillation head . Grease the ground-glass joints of the distillation head lightly and place the head on the flask. It is generally not necessary to clamp the head. (Do not attach the thermometer at this time). 3) The condenser . Grease the ground-glass joints of the condenser lightly and attach rubber tubing firmly to the jacket inlet and outlet (which should not be greased). A strong clamp (oversized, if available) is needed to hold the condenser in place. Because of the weight and angle of the condenser it will tend to pull away from the distillation head. For this reason, check the tightness of this joint frequently before and during a distillation. Attach the rubber tubing from the lower end of the condenser to an adapter on the water faucet.
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Expt 03 - Simple and Fractional Distillations - EXPERIMENT...

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