# Experiment to determine the ethanol content of wine

## Experiment to Determine Ethanol Content of Wine

The purpose of this experiment is to determine the ethanol content of each of the wines and compare the value determined to the value quoted on the label. These results can then be used to conclude which region is more accurate in quoting the value of the ethanol content of the wine.

This experiment takes advantage of the fact that ethanol is less dense than water in solution. The density of ethanol at 20°C is 0.789 g/cm3 while the density of water at the same temperature is 0.998 g/cm3. It then follows that different solutions of ethanol and water will have different densities also, because the relative volume of ethanol increases and water decreases so the density of higher percentage ethanol solutions will be less than the density of lower percentage ethanol solutions. This occurs because water molecules are much smaller than ethanol molecule, meaning more water molecules can “pack” into a smaller volume than ethanol molecules, meaning there is more mass per unit volume of water compared to ethanol, meaning it has a higher density.

In this experiment, solutions of ethanol in water were made up, going from 0% to 20%. These were then weighed, and the density of the ethanol was calculated. From this, a graph of percentage ethanol solution against density was made. This graphs later compared to the density of the wine, so the percentage ethanol of the wine can be read off the graph.

The samples of wine are then distilled, in order to extract the ethanol from the sample. Before distillation, the wine is made alkaline using Sodium Hydroxide. This is because the solutions of ethanol used in order to make the ethanol concentration against density calibration graph contained ethanol and water only, and it the sample of wine was not made alkaline then many of the volatile acids contained in the wine would distil off and affect results.

The sample of wine was distilled to 100°C, to ensure all of the ethanol is distilled from the sample. This is because the boiling point of ethanol is 78°C, and at 100°C is when water begins to be distilled off, so the distillation is stopped there. Because water is to be added to the sample to make it the same volume as the solutions used in the calibration graph, it does not matter if a small amount of water is distilled over here.

A pH meter had to be used to determine when the wine turned alkaline. To calibrate the pH meter, a pH 7 solution was made up using a pH 7 buffer tablet and deionised water then the instructions for the pH meter were followed carefully in order to calibrate it.

## Procedure

Chemicals

• Deionised water
• Ethanol
• 3 white wines from different regions
• 0.1M Sodium Hydroxide
• pH 7 buffer tablets

Apparatus

• pH meter
• Density bottle of known volume
• Balance accurate to 3 decimal places
• Distillation apparatus
• Heating Mantle
• Dropper
• Anti bumping granules
• Burette
• Measuring pipette
• Measuring cylinder
• Beaker