Taylor Small
09-23-13
Lab Report: Determination of Alcohol Content

Blame it on the Alcohol

Objective:
Boiling is a process familiar to anyone who has cooked pasta or brewed tea. As heat is applied to a pan of water, the temperature of the water increases until it reaches 100°C (212°F). At this temperature, additional heat causes the water to bubble vigorously as the liquid water is converted into gaseous water, or steam. Most organic liquids will behave in a similar fashion. On heating, the temperature of the liquid increases until the boiling point is reached. Additional heating causes the liquid to vaporize accompanied by vigorous bubbling of the liquid. The boiling point of a substance is a physical property of a substance and can be useful for characterizing that substance. The fact that different substances have different boiling points allows us to separate them. The process of heating a substance until it is vaporized, cooling the vapors, and collecting the condensed liquid is the basis of a commonly used purification technique called distillation.

Method:
The fractional distillation apparatus was set-up as shown in the illustration and was approved by the TA. 50 mL of wine was added into the flask along with boiling chips and the flask was then placed into the heating mantel. A flow of cold water was set-up to continuously run through the condenser and the variac box was set to 5. The temperature at the distilling head was measured and recorded for every mL of distilled ethanol collected. This process continued until 25 mL was collected, and then all waste was cooled and poured down the drain.

Data and Results:

Figure 1.1: Temperature determined at distilling head after every mL of distilled ethanol was collected.

(See data sheet for more calculations)

Conclusion:
Approximately 24 mL of distilled ethanol was collected before the temperature rose to over 100 °C. Therefore, the measured ethanol percentage in the wine sample was 48%. Compared to the 11.5% ethanol content listed on the wine bottle, there was a 76% error between the experimental and actual value. Experimental error could be caused by the single distillation performed, as well as the low concentration of alcohol in the original sample.