Gas Flow Analysis
C6H12O6 --> 2 C2H5OH + 2 CO2
Since the ratio of ethanol produced to carbon dioxide produced is constant, it is possible to measure the rate of ethanol formation by measuring the rate of carbon dioxide formation. At standard temperature and pressure (approximately room temperature and sea level pressure) for every liter of carbon dioxide gas that is produced, approximately 2 grams ethanol are produced, which is approximately 2.5 milliliters of ethanol.
Measuring the rate of gas flow from a fermenter is fairly easy. All you need is a bottle, some tubing, a pot, and a bit of water. First fill the bottle completely with water, next add enough water to the pot so that the opening in the bottle will be completely covered when the inverted bottle is placed in the pot. Put the bottle in the put and use the tubing to connect the fermenter to the bottle. Finally, time how long it takes for the bottle to be completely empty of water.