Simple and Fractional Distillation - Determination of Solution Composition

Experiment 2 Simple and Fractional Distillation - Determination of Solution Composition Introduction Distillation technique will be used to separate a solution with two known, miscible liquids. The difference in boiling points of the two liquids and using a complex glassware apparatus will cause the separation. The two miscible liquids in the solution will be identified, and the specific solution composition/ratio of liquids will also be determined. Both simple and fractional distillation will be used in order to test which is more efficient according to this experiment. Simple distillation is most effective when separating two liquids with different boiling points, whereas fractional can be used to separate mixture with multiple components as well as various boiling points even if they are similar. Table of Reagents Compound Structure MW (g/mol) BP (℃ ) Densities (g/cm^3) Methanol 32.04 64.7 0.7918 Ethanol 46.07 78.37 0.789 Water 18.02 99.98 1 Safety ● Caution must be exercised at all times especially when working with hot glassware. ● Be careful to never heat a sealed vessel and always make certain to add boiling chips to any liquid before heating. ● Both methanol and ethanol and highly flammable, be sure to avoid sparks, flames, and hot surfaces. ● Do not inhale any fumes. ● Avoid letting methanol and ethanol come in contact with skin and eyes. ● Once the apparatus is fully cooled, it can be dismantled. Report any liquid or vapor exposure to TA immediately. ● Dispose of all liquid waste in labeled bottle in the hood. Experiment Procedure 1) Simple Distillation a) Simple distillation will be conducted by one of the groups on an unknown binary solution. Place 21 mL of the solution into a 50 mL round bottom flask along with several boiling chips. b) Construct a simple distillation apparatus and begin boiling the solution. c) Use the Variac voltage controller attached to the heating mantle to regulate the heating of the distillation flask so that approx. 1-2 mL of distillation per minute can be collected. i) Do not simply turn the dial “10” from the outset. ii) Rushing a distillation will result in poor segregation and a longer stay in the lab. iii) As the solution begins to boil, there will be progress in the vapor as it moves up into the still head, from there into the condenser, and finally into the catch flask/cylinder. d) Record the temperature of the first drop of distillate collected and then the temperature of each millimeter collected during the course of the experiment. i) All 21 mm of solution do not have to be collected in the receiving cylinder. Instead, collect 18 mL of distillate (19 data points) and then remove the boiling flask from the heating mantle in order to begin cooling the apparatus to room temperature. ii) Make sure glassware has cooled completely before dismantling the system. Remember the methanol vapors are toxic and must be avoided. 2) Fractional Distillation a) The second group will collect a Variac voltage controller and plug the heating mantle into it and the controller into the wall. The heating mantle should never be plugged directly into the wall outlet. b) Attach the heating mantle to a ring stand found in front of the room. c) Adjust the heating mantle’s height to best control the heating of the flask. d) Place an iron ring above the mantle attached to the ring stand and cover it with wire gauze. e) Pour 21 mL of the solution into a 50 mL round bottom flask along with several boiling chips. Be sure to add enough solution to the flask for continuous boiling over 20 min. f) For the group conducting fractional distillation, put steel wool on the inside of the fractional column and using vacuum grease on the associated joint attach it to your round bottom flask. g) Clamps should then be promptly placed around the previously mentioned joint and the top of the fractional column for support. h) Next, attach the distillation head to the apparatus. This varies depending on the type of distillation given to you to perform. i) For simple distillation attach the round bottom flask to the still head and secure it with a ring clamp after having applied vacuum grease. ii) For fractional distillation attach the still head to the top of the top of the fractionating column and place a thermometer either inside the built in holder or a tapered thermometer adapter. Grease the side arm of the still head and attach the condenser. Support the condenser with ring clamp and stand. Attach the lower arm of the condenser to the water valve with a vacuum tube. Add a hose to the upper arm of the condenser. This will be the “water out” hose. Use only a low water pressure during distillation. A steady drip or trickle of water is desired. Add vacuum grease to the condenser’s end and attach the short stem funnel. Place the 10 mL graduated cylinder below the short stem funnel to collect the condensed droplets. The apparatus is now complete. i) Begin distillation by heating the solution to a gentle boil. Too vigorous a boil could cause the liquid to deplete too quickly ending the distillation prematurely, cracking glassware. 1-2 mL of distillate per minute is ideal.