Liquid Liquid Extraction We were asked to extract benzoic acid from a mixture of kerosene and benzoic acid. This had to be done using the stirred liquid-liquid extraction column in the senior laboratory. Fresh water was used as a continuous phase in the extraction. We were asked to measure benzoic acid concentrations in the feed, refined and extract streams. These measurements had to be made in several different steady states. The number of theoretical steps and the height of the theoretical steps (HETS) also had to be determined. Since the liquid-liquid extraction column had not been used for several years, our task also included discussing any process-related problems and possible solutions. Discussion of the equipment, results, and experimental procedure will be discussed in the following paper titled “Liquid-Liquid Extraction.” Even though the process was not used for several years, everything worked very well. The flow meter used to measure the water had a small leak that was easily fixed using a bucket. One of the storage tanks still contained approximately 400 liters of kerosene with a benzoic acid concentration of 0.00208 (gm/mL). benzoic acid in the aqueous extract was 0.00109 (gm/mL) and 0.000783 (gm/mL) for two separate steady-state experimental analyses. The kerosene feed flow rates for the two steady states were 0.361 (gal/min). and 0.157 (gal/min) respectively. The number of theoretical stages for flow rates of 0.361 (gal/min) and 0.157 (gal/min) were determined to be 1.76 and 0.87 stages, respectively. 48.9 in. The HETS for the two steady-state conditions was 27.71 inches and 56.42 inches respectively. The transfer of benzoic acid from kerosene to water was accomplished without major problems. The equipment worked very well, except for small problems with the water flow meter. After working on the process, we recommend using it more often. We also believe that the results obtained from our experiments are accurate and well below experimental error. SUMMARY Liquid-Liquid Extraction of Benzoic Acid The number of theoretical stages and the height of equivalent theoretical stages were determined for a liquid-liquid extraction process...... .middle sheet...... state conditions of having given good separations. We also believe that the correlation between the pH of the aqueous benzoic acid solution and the actual concentration of the acid is accurate. We recommend using the liquid-liquid extraction column more in the senior laboratory. The process is very interesting and seems to work well.NomenclatureSymbol Definition UnitXf Concentration of benzoic acid in the feed kerosene (gm/mL) )m slope of equilibrium line dimensionse extraction factor dimensionsN number of theoretical stages dimensionsZt effective height of experimental column (inches)HETS height of equivalent theoretical stages (inches)ReferencesRobbins, L.A., “Liquid-Liquid Extraction,” in Perry's Chemical Engineers' Handbook, sixth edition, D. Green and R.H. Perry, McGraw Hill, New York, NY, p 51-1, (1984) Allerton, J., "Liquid Extraction in Perforated-Plate and Packed Towers." American Institute of Chemical Engineers. 39:361-384 (1943).