A Large-Scale Laboratory Extractor of the Soxhlet Type KARL E. RAPP, C. W. WOODMANSEE, AND J. S. MCHARGUE Kentucky Agricultural Experiment Station, Lexington, Ky.
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N CHEMICAL investigations of agricultural products it is
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frequently necessary to extract large quantities of material. This problem was encountered b y the authors in an investigation on tobacco and its solution may be of use in other laboratories. The extractor was designed and constructed from two alcohol drums and other materials obtained from a plumbing shop. In Figure 1 the distilling pot, 1, is made from a 55-gallon drum. Heat is supplied by a steam coil entering a t valve 2. The solvent vapor tube, 3, made of 2-inch iron pipe and fittings? is welded to the drums. A 30-gallon drum comprises the extraction chamber, 4, with 0.5-inch pipe and fittings for the siphon tube return, 5 . Coupling joints are provided for both vapor tube and siphon tube for ease in handling. Condensation is maintained by a spiral cone condenser head, 6, with auxiliary straight tube condenser. 7. connected in series to the water line. A steamradiator sh&y valve, 8, is attached to 7 when the air has been forced from the system. This prevents air from bemg drawn in by the partial vacuum created each time the extract siphons over, resulting in the loss of solvent. A detailed diagram of the condenser-head assembly is shown in Figure 2. The drumheads are cut out and flanges welded to the sides. The extractor heads are bolted to thqse flanges, being sealed with braided graphite-impregnated packing. Thus they
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FIGURE 2. CONDENSER-HEAD ASSEMBLY are removable for charging and cleaning. An ordinary IS-inch boiler gage, 9, provides a means for following the solvent level in the pot. The pot steam coil is so placed that the solvent level never falls below about 5 gallons, automatically preventing the extract from becoming overheated. The ground material to be extracted is held in a heavy cotton bag double-sewn a t the seams, which is supported on a small rack, 10, made of iron piping welded at the joints. When extraction is complete the distilled solvent and concentrated extract solution are drawn off a t taps 11 and 12, respectively. Following this operation the straight tube condenser, 7, is connected for distillation by means of adapter 13, the spiral cone condenser being disconnected from the water line. Steam through valve 14 is then used to distill the solvent from the extracted residue in fhe bag. Solvent vapor passes to the condenser and also in reverse direction through the vapor tube, 3, and is condensed. That returning to the distilling pot serves to rinse down the sides of the drum. It is drawn off and added to the concentrated extract for final solvent recovery. The capacity of this apparatus is approximately 50 pounds of dried plant material. With this charge the solvent requirements are 25 to 35 gallons, most of which is recovered after extraction. Experiments in the last year have proved the efficiency of the extractor. THEinvestigation reported in this paper is in connection with a project of the Kentucky Agricultural Experiment Station and is published by permiasion of the Director
FIGURE 1. DIAGRAM OF APPARATUS
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