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.
Clamp the flask assembly into the beaker so that flask is as far down as possible in the beaker. Heat at the boiling point of water until liquid is no longer visible in the flask. Continue heating for another 10 minutes. Measure the temperature of the gas occupying the flask by recording the temperature of the boiling water surrounding the flask to the nearest +-0.1 since the flask is even so slightly open to the atmosphere, the pressure of the gas must be equal to the barometric pressure. Measure the atmosphere pressure with the barometer in the laboratory and record the current barometric pressure on the report form.