[ Plan ] [ Schematics ] [ Procedure ] [ Raw Data ]

1. Pour the 1-propanol-water mixture from the three containers (labeled 1, 2, 3) into the white bucket and mix them up with the aluminum stirring rod. Withdraw a few c.c. of the liquid with a dropper and analyze the concentration by the refractometer (read the procedure for using the refractometer).

2. The mole fraction of the 1-propanol should be above 80% (refer to the refractive index calibration curve posted). If mole fraction is too high (e.g. close to 100%) try to dilute it with distilled water and analyze it with the refractometer. Use a small quantity only. This is to avoid over dilution of the 1-propanol. Repeat the procedure until you reach a refractive index reading of about 1.3822.

3. After the desired concentration of 1-propanol is reached, measure 5 to 6 liters of the solution and pour it into the still pot with a funnel through the port where thermocouple no. 1 is placed. Use great care when you remove the thermocouple from the pot and avoid bending it or it might break.

4. Plug in the digital thermometer and switch it on. The knob on the right side of the panel indicates the designated thermocouple hooked up with the distillation column. No. 1 is for the still pot, 2 for the 1st tray, 3 for the 2nd tray and so on. A total of 7 probes are used. Try to trace them on the distillation column and turn the knob to see the temperatures at different locations.

5. Turn on the flow of water in the condenser. Plug in the two variacs which control the quantity of heat delivered to the heating mantle. According to previous groups' experience the proper setting should be about 80 to start. Full power for lower heater. With these settings you should be able to establish a temperature gradient in the column. Use total reflux for this part of the experiment. Steady state is achieved when the temperature readings do not change with time. When this happens, record all temperatures.

6. Once steady state and temperature gradient are established at total reflux, take a sample (couple of c.c.) from each tray with a syringe through the port where the septum is located. Dry the syringe with air after each sampling. Analyze the collected sample with the refractometer. Take several readings of the same sample to ensure correct readings. Also withdraw a few c.c. from the pot by siphoning the liquid out with a rubber bulb and analyze it. Record the total quantity of liquid used. Pour the waste liquid back into the containers (1, 2, or 3).

1. Turn off the heating coils for the column.

2. Wait 30 minutes (or as long as it takes) for the column to cool and drain into the stillpot.

3. Start the flow of cooling water through the bottoms condenser. It will be used to cool the bottoms as they are withdrawn.

4. Start the suction device connected to the trap located after the condenser.

5. Using the suction, establish gravity flow of the bottoms from the stillpot. Once flow has started, turn off the suction as it removes a great deal of alcohol vapor from the bottoms. The trap should be in an ice-water bath to cool the bottoms.

6. When no more flow of bottoms occurs in Step 5, drain the remaining bottoms with the tube-and-syringe set-up.

7. Remove the contents of the vapor ports into a beaker, and then add all the liquid removed into one closable vessel.

8. Turn off the column and bottoms condenser.

N O T E: At all times, avoid leaving alcohol solutions exposed to air. Cover the container.

1. Lift and pivot the top cover of the prism so that you can see the rectangular prism surface. Clean the surface with tissue paper if it is dirty.

2. Place a couple of drops of 1-propanol-water solution on the surface of the prism.

3. Cover the prism surface with the top cover gently. As you push the top cover down on the prism you will hear a "click" sound.

4. Turn on the toggle switch located on the left side of the refractometer and adjust the light source by moving it up towards the prism.

5. When you look into the eye piece, you will see an orange rainbow pattern on the upper half of the circular field.

6. Focus the lower edge of the orange pattern with the dial that is located above the prism on the body of the refractometer. For 1-propanol-water mixture, the proper range should lie between 18 and 25. Adjust the lower edge of the orange pattern so that it passes through the cross by turning the metal knob (hand wheel) that is located on the right side of the refractometer. By pushing the toggle switch down the orange pattern will disappear and a scale will appear to show the refractive index.

If you have trouble with focusing the orange rainbow pattern, it could be due to one of the following reasons:

1. Part of the liquid is evaporated and the liquid film is unevenly spread on prism surface. You should clean the prism and reapply the liquid.

last update: 03/18/99