Purpose: To measure the amount of alcohol in a commercial product.

Background:

Distillation is a process for separating mixtures based on the boiling points of the components. The lower boiling substance is boiled off first and then higher boiling components follow. Alcohol is lower boiling than water and should distill from your product first. However, it is not possible to get a clean separation of alcohol from water. Therefore, the resulting solution will be a mixture. You will use the density of the mixture to estimate the volume of alcohol in the original sample.

Experimental:

Gather the equipment and set up the distillation apparatus as in the demonstration or follow the instructor’s directions.

Carefully measure about 50 mL of your commercial product into the 125 mL round bottom flask. Add 25 mL of water and 2 to 3 boiling stones. Slowly heat the solution until the temperature reaches 98 ° C. Carefully measure the total volume of distillate that you collected. Measure the density of the distillate. From the density of the distillate, calculate the volume of alcohol in the distillate. If all of the alcohol came from the 50 mL sample of your commercial product, what is the percent alcohol by volume in your commercial product?

Confirm the presence of alcohol in your distillate. Add one drop of chromic acid reagent to 1 mL of acetone in a small test tube. Observe the color. It the color turn green, do not use the acetone. Add 1 to 3 drops of the distillate to 1 mL of acetone. Then add one drop of chromic acid reagent. A green color is a positive test for the presence of alcohol.

Goal: To test at least two different conditions that could affect the amount of alcohol generated by yeast.

Experimental:

Each student must prepare at least two samples of "moonshine". The goal is to change an experimental variable to see how the variable affects the amount of alcohol produced. Possible variables include:

source of sugar (juice, glucose, sucrose, etc.)

temperature

pH

water source (distilled vs. tap, etc.)

other student generated ideas

Measure about 500 mL of water. Heat to roiling boil to dissolve the sugar source. Cool to 70 ° C before adding yeast. Measure about 3 g of yeast for each sample. Add the yeast, swirl to mix and cover your flask with a rubber glove. Allow to sit for one week. Predict which of your samples you expect to produce the most alcohol and why.

May use alternative method in which about 10% sugar solution is used with Na₂PO₄ is used. Requires one week to ferment.

Carefully measure about 50 mL of your product into the 125 mL round bottom flask. Add 25 mL of water and 2 to 3 boiling stones. Slowly heat the solution until the temperature reaches 98 ° C. Carefully measure the total volume of distillate that you collected. Measure the density of the distillate. From the density of the distillate, calculate the volume of alcohol in the distillate. If all of the alcohol came from the 50 mL sample of your product, what is the percent alcohol by volume in your product?

Confirm the presence of alcohol in your distillate. Add one drop of chromic acid reagent to 1 mL of acetone in a small test tube. Observe the color. It the color turn green, do not use the acetone. Add 1 to 3 drops of the distillate to 1 mL of acetone. Then add one drop of chromic acid reagent. A green color is a positive test for the presence of alcohol.

Repeat the procedure with your second sample.

Is there a difference in the amount of alcohol produces? Explain.