Distillation+Lab

In the laboratory, distillation is performed as a means of purifying and identifying organic compounds. In the distillation process, an apparatus is set up so that a distillation flask is connected to a water-cooled condenser, which is connected to a receiving flask so that everything is sealed except for an open chamber on the end piece, depressurizing the system. A liquid mixture is distilled by heating it in the distillation flask so that it vaporizes. The vapors are then condensed in the water-cooled condenser that captures the vapors and cools them to a liquid state. The distillate then drips into the receiving flask. A simple distillation involves only one cycle of the distillation process. Distillation is most efficient when the impurities in the liquid solution are non-volatile or have very high boiling points so that no impurities get into the distillate. The desired compound to be distilled is best purified when it has a lower boiling point than its other constituents in the starting liquid (around a 70 degrees C difference). If the compound to be distilled has a boiling point similar to its constituents, then it may take several distillation cycles to come up with a pure compound. As well, if the compound to be distilled is fairly pure to start with, simple distillation is a good tool to further purify the compound. The boiling point of a compound can also be determined through distillation, which is an important identification tool..The boiling point is measured by means of a thermometer placed and sealed within the distillation flask that measures the temperature of the vapors boiling out of the liquid. This measures just the desired compound's boiling point temperature and not the other substances that are in the liquid. To verify the purity of the distillate, the boiling point reached in the experiment can be compared to values found in the Merck index. The sample can also be analyzed by infrared spectroscopy.
 * Introduction **

nicely done.

Letcher, C. “Simple Distillation: Purification and Reuse of Acetone.” Green Chemistry. Web. 29 October 2010. []
 * Procedure **

Graph of temeperatures over course of acetone distillation and corresponding table: - The initial temperature at which acetone started to boil out of the impure solution was 50°C with a flow rate of under 1 drop per second initially to approximatley 2-3 per second in the last half of the distillation process.
 * Data / Analysis **

- The final temperature reached was 54.9°C after 28.5 minutes of distillation. The distillation was stopped here as less than 5 ml of impure acetone remained in the initial distillation flask. The last three data points on the graph and table were accidentely recorded as the lab quest was not stopped after the heat source was removed from the distallation apparatus.

- Impurities could be seen in the starting flask as the liquid contained in it was a white murky color.

- The boiling temperature of acetone, is 56.5°C (The Merck Index, 2001). This temperature was never reached.

- The final volume of pure acetone recovered was 36.7 mL which, out of a starting volume of 40.0 mL, which is an 91.8% yield.

-The percent yield was derived from dividing the recovered acetone by the total volume of contaminated acetone, which is only a percent measure from the entire sample volume. Since it is unknown how much acetone versus impurities were actually in the starting solution, a percent yield cannot be derived for acetone alone.

good good good!

- As shown by the above graph, many of the valleys of transmittance coincide with those observed in our sample, though the valleys between 1500 - 1000 are much more pronounced than we observed. The sharp valley at 550 and lesser valleys at 3000 and around 3500 were not recorded in the IR spectrum of our sample. As well, the recovery had slight transmittance at 2300, and this is not shown on the above graph. This shows that the recovery sample had a slight impurity -The boiling point of the recovered acetone was lower than The Merck Index recording for acetone because the difference in elevations has plays a part in the pressure of the atmosphere causing boiling points to slightly alter.
 * Acetone theoretical spectral data** (source: []):
 * Groups Spectral Analysis**:

The purified acetone product, despite having a lower boiling point than recorded in the Merck Index, matches up with spectral data almost perfectly. As noted, only a small shift from wavenumbers 2100 to 2300 can be recognized as a sign of impurity. This relative purity shows the effectiveness of distillation as a method of separating substances. The accuracy of this procedure could be better tested by taking samples of the distilled product from different temperatures and observing the spectral data for differences in transmittance.
 * Conclusion **

can you comment about the range of temperatures over which the substance distilled? What does that tell you about purity? And.....error? Post-lab Question?

Other than those criticisms this is a darned nice report.