Create a hot water bath by filling a 600 ml beaker half full of water. Heat to boiling on a hot plate, and while waiting for the water to boil, use a 10 ml graduated cylinder to measure and pour approximately 2 ml of your liquid unknown sample into the flask. Secure the aluminum foil over the mouth of the flask with the rubber band. Make a tiny hole in the foil with a pin to let excess vapor escape during heating.