Summary Two basic methods have been presented for measuring the rate of extraction of crude lipids from “oil”‐bearing materials with solvent. In the Percolation Method the extraction is carried out by percolating fresh solvent through the sample and measuring the “oil” recovered at succeeding time intervals. In the Batch Co‐current Method samples of miscella are withdrawn periodically from an agitated batch of known quantities of oil‐seed and solvent and analyzed for lipids to check the progress of the extraction. These methods have been used successfully in the Blaw‐Knox laboratories over the last four years in making studies of factors influencing equipment design and plant operation as well as fundamental studies contributing to a general understanding of extraction. Some of the “oil”‐bearing materials which have been studied using these methods include: soybeans, cottonseed, peanuts, flaxseed, corn germ, castor beans, wheat germ, rice bran, mowrah seeds, tung nuts, grain sorghum, and various expeller and press cakes. Special studies include methods of preparation, temperature effect, moisture content, nature of solvent, varieties of seed, and particle size.

Summary The temperature has a considerable effect on the rate of extraction of crude oils from vegetable oil seeds with solvents. Quantitative data have been presented relating extraction rate and temperature for soybeans, cottonseed, and flaxseed extracted with several solvents. These data were obtained by the Percolation Method, modified where necessary. Since no satisfactory theoretical basis for correlation could be established, the results were correlated empirically. For all practical purposes the time in minutes required to reduce the oil seed to 1.0% residual oil content on a dry basis varied inversely with the square of the extraction temperature in degrees Fahrenheit.

Summary Quantitative data have been presented for the effect of “effective extraction size” on the rate of extraction of oil from soybeans, peanuts, cottonseed, corn germ grits, and flaxseed. Both flakes and grits have been studied. The results are best correlated by a straight‐line plot on log‐log paper of “time to 1% residual” and effective extraction size. The slope of the line is a measure of the change in extraction rate with extraction size. The slope was found to be different for the different oil seeds and to be larger for seeds prepared as grits than for the same seed prepared as flakes.

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Summary The general trend in the industry is toward solvent‐extraction recovery and to larger plants. Technological change in recent years has been largely in improved equipment and process improvements to decrease operating costs and improve product quality. It is the author's opinion that the trend mentioned above and this type of technological change will continue in at least the near future. It is expected that any radical change in processing will come about only by a radical change in raw material or products desired rather than by the development of really new equipment or process methods. One interesting development in recent years is the increasing relative importance of the residue solids compared to the oil in the case of some of the materials. Plants have been built primarily as a source of protein rather than oil in certain cases. It also accounts for the incidence of some small plants in the raw material “fringe” areas contrary to the general trend.