The object of this investigation was to determine the transfer coefficients based on a “no loss” material balance, Viscosity Gravity Constant for each extraction and the contact area in conjunction with the material balance when a cylinder stock out of midcontinent oil was subjected to furfural refining in a one-inch in nominal diameter pyrex glass spray column using various ratios of furfural to oil. The oil was passed in tiny drops through the 9.75 feet high column countercurrent to the furfural flow which was down through the column. The average number of drops formed and the time of contact with the solvent was determined. From these values the average contact area in square feet at any moment was calculated. Two runs were made at high ratios of furfural to oil, and in these runs, no area of contact was determined. The column extractions were carried out at 75 ± 3°F. In order to determine the equilibrium values necessary for these calculations, batch extractions using the same ratio of solvent to oil were carried out at 230°F—at which temperature the furfural and the oil were miscible. The ratios of furfural to oil used were 2.35, 3.00, 3.53, 5.20, 9.24 and 14.20. The values of the transfer coefficient based on the “no loss” material balance varied from 0.0427 to 4.59 lbs./hr./cu.ft. of column volume/unit C as the ratio was increased. The values of the transfer coefficients based on the Viscosity Gravity Constant varied from 0.0520 to 6.28 lbs./hr./cu.ft. of column volume/unit C as the ratio was increased. The values of the transfer coefficient was based on the “no loss” material balance and the calculated contact area varied from 0.390 to 1.168 as the ratio was increased. The resultant values of the H.T.U.’s based on the three methods of calculation were good checks for the first two ratios and fair checks for the next two highest. For the ratio of 2.35:1.0 the H.T.U. based on the “no loss” material balance alone was 1.15, on the V.C.C. for each extraction it was 1.4 and for the method utilizing the contact areas and the “no loss” material balance it was 1.08 feet. The best batch refined oil had a viscosity index of 85. The best column refined oil had a viscosity index of 73.5. In both cases these values were reached using a ratio of 5.2 parts of furfural to one part of oil by weight and subsequent increases in this ratio did not improve the properties. / Master of Science