It is also important to know the height of the equivalent theoretical stages. The graphical method requires an equilibrium curve for the three component system and an operating line which shows the actual separation achieved by the system. By stepping from the operating line to the equilibrium curve the number of theoretical stages can be determined. This method will be described in greater detail in the next section. III. Apparatus and procedure.The main objective of the experiment was to determine the number of theoretical stages and the height of the equivalent theoretical stages (HETS). Benzoic acid was to be transferred between kerosene and water and measurements of the concentration of benzoic acid in the feed, raffinate, and extract were to be measured. Because the process had not been used in several years we first looked the equipment over to determine how it worked. The basic process consisted of an extraction column, four storage tanks, and a pump. The column itself contained 10 stages with impellers between each stage. The impeller speed was set to 360 revolutions per minute. This impeller speed was chosen purely at random. The top of the column contains an inlet for the water and a outlet for the raffinate. Conversely the bottom of the column consisted of an outlet for the extract and an inlet for the kerosene feed. Both of the inlets came directly from pumps which pulled the kerosene feed and the water from there respective storage tanks. The outlets were piped directly to the raffinate and extract storage tanks. The piping was designed such that there is a place to take samples from each of the pipes entering and exiting storage tanks. After studying the equipment we determined the contents of the kerosene feed tank. The tank contained approximately 400 liters of a kerosene-benzoic acid solution with an unknown concentration. To determine the concentration we mixed a measured amount of the kerosene fee...
