Method and Equipment

                To experimentally observe compounds at the phase equilibrium between liquid and gas a specific type of isolated system is required.  An apparatus created by Dr. Sandor Kadar was suitable for this use. The apparatus was set up with a closed metal chamber (reaction vessel), and a slow heating unit suspended in a chamber allowing for a water bath around the system. The metal chamber has two valves, one attaching to a GLX connected to a computer running the program Data Studio to monitor the experiment and one that can be opened to allow for the introduction of a compound. The heating unit allowed for significantly slow heating.

                 To begin the experiment the metal chamber was attached to a vacuum pump through the valve of the reaction vessel to ensure that it was empty of any substance and had a true vacuum. After, 30 mL of the compound of interest was put into a syringe, attached to the valve and put into the reaction vessel, making sure to not allow any air to enter. The substance was then allowed sufficient time for it to obtain an initial equilibrium between the two phases (liquid and gas) in the chamber.

                  Once equilibrium is obtained, the heating unit was turned on and a run was started on Data Studio to record the pressure and temperature of the reaction vessel overtime. The heat of vaporization is temperature dependent but if small changes in temperature occur it can be considered constant. The heating unit slowly increases the temperature of the water cath over time. Data studio was set up to record a graph of the natural log of the pressure against the inverse of the temperature at a given time. This was run for approximately one and a half to two hours depending on how the data looked (a straight line on the graph is ideal). The temperature of the reaction vessel was not allowed past the boiling point of the substance being tested.

                  This procedure was performed for each of the three compounds that were tested (Ethyl acetate, Isopropyl alcohol and Diethyl ether). Compounds that have low boiling points, like Diethyl ether, require that the temperature of the water bath surrounding the system be fairly low in order to gain enough data points before the system reached the boiling point of the substance. This was done by adding ice to the water bath and allowing the bath to get to a lower temperature before the substance of interest was introduced. Once each run was finished the data was recorded and the slope of the graph of the natural log of the pressure against the inverse of the temperature at a given time was obtained. This slope allowed for the calculation of the heat of vaporization for each compound.