Distillation - Christopher King：蒸馏-克里斯托弗王.doc

Simple and Fractional Distillation, and GC AnalysisName:Date: Desk no.: Partner:Physical PropertiesMM, g/mold, g/mLmp., Cbp., CCommentscyclohexanetolueneObservationsDistillation results: Distillation Temperature/C vs. Volume/dropsdropsSimpleFractionaldropsSimpleFractionaldropsSimpleFractionaldropsSimpleFractionaldropsSimpleFractional11529435721630445831731455941832466051933476162034486272135496382236506492337516510243852661125395367122640546813274155691428425670QUESTIONS (Nearly all answers can be found in the 1st 6 pages of chapter 5) 1. A certain liquid boils at constant temperature, for example 127C. Based on this boiling point alone, is this a pure liquid or not? Explain.2. Explain why a packed fractionating column is more efficient than an unpacked one.3. What is the effect on the boiling point of a solvent (e.g., water) produced by a soluble nonvolatile substance, such as sodium chloride?What is the effect of an insoluble substance, such as sand or charcoal?What is the temperature of the vapor above these two boiling solutions?4. Why is it extremely dangerous to attempt to carry out a distillation in a completely closed apparatus (one with no vent to the atmosphere)?5. What effect does the reduction of atmospheric pressure have on the boiling point? Can cyclohexane and toluene be separated if the external pressure is 350 mm Hg instead of 760 mm Hg?Procedures: In the textbook, pp. 89-90.2.(A)Simple Distillation of a Cyclohexane-Toluene Mixture3.(B)Fractional Distillation of a Cyclohexane-Toluene MixtureChanges and Notes:General:Boiling chips are on the center tables. Most of the Viton connectors we use are whitish, not black. A picture of a claisen head is given on p. 10, item j. To heat the assembled apparatus, use a sand bath in a crystallization dish placed on the hot plate. The sand only needs to be 1/4” to 3/8” (5-8 mm) deep; if too much sand is used, you have to wait for it to warm up. A hot plate setting of 6 or 7 will probably do the job.gc analysis: Samples will be analyzed by gas chromatography (gc). Obtain six vials and lids from the cart at the front of the lab. Collect the first 5 drops of the distillation in one vial, then cap it. Collect the rest of the distillation in a second vial. Let the apparatus cool, then transfer the undistilled liquid into a third vial, and cap it. The contents of the first and third vials will be analyzed by gc (nothing is done with the third vial). The procedure says to stop collecting liquid when about 0.4 mL remains. You will just have to estimate when that point is reached. Likewise, use three vials to collect the liquid from the fractional distillation. 2.(A)Use a 50 mL beaker to hold the vial and ice (we dont have 30 mL beakers).3.(A)Note that ice isnt called for in this procedure.An Excel spreadsheet is on the computers for graphing the results. Not every point needs to be entered.Empty your mixtures into the waste container (the instructor will show you which hood it is in). Place the empty vials with the lid off on the piece of paper in that hood.Equipment:72 vials with lids(vials and lids are reused by each section)12 towel “quarters”, + one for the example setup1 box of rubber bands (for holding the towels around the fractionation columns)two metal scrubbers (used to pack the fractionation column). May want to put a box of scrubbers on the bottom shelf in case they get used up.2 pairs of scissors for cutting up the scrubbers1 800 mL beaker labeled “cyclohexane & toluene waste” (Leave in hood until waste evaporates.)Have simple and fractional distillation setups ready (on front desk so students will know how to put the glassware together.2 125 mL Erlenmeyer flasks with cork stoppers. Label one “cyclohexane” and the other “toluene”. Fill half full with these solvents.2 5 mL autopipets. They will be set at 2 mL, and should be have the same labels as the flasks (above).1 vial containing 2 mL of cyclohexane and 2 mL of toluene. Label it “1:1 toluene + cyclohexane”.Store the original bottles of cyclohexane and toluene on the bottom shelf of the cart so that the Erlenmeyer flasks can be refilled. Total needed for one section of lab: 65 mL of each (includes 30% “spillage allowance”)4 10 L syringes (probably stored in the instrument room)4 computers, printers, and gas chromatographs. The gc may be placed on the top of the small computer carts, along side the monitor. (Cant do that for the large cart.) Instructor: Show how to use autopipets to get the solvents.Explain gas chromatography, and show how to inject into the gc. The recommended procedure is to draw in 1 L of air, then 1 L of sample, then another 1 L of air. Measure this at the tip of the syringe plunger; ignore the presence of liquid near the tip. Press space bar to start the run. (The End key on the keyboard may be pressed to end a run before the programmed end.)If the gcs have been used for other purposes, they will need to be initialized. To do this, turn on the gcs, then start the “PeakSimple” software. On the File menu, select Open control file, and select “”. Also, you may need to select the temperature program file, “cyclohexane, toluene.tem” (Click the button that looks like 1234 thats the temperature iconand select th