A Simple Continuous-Extraction Apparatus' By A. 11. Clark sc,ioo,. "B YHAauacu, UhilVBaSlr" o n ILLINOIS, C,liC,iOU, ILL.
N NUMEROUS occasions the writer has been called upon to extract relatively large aniounts of ground vegetable drugs with volatile solr~ents. h Soxhlet extractor of sufficient size, more than 100 grams, is rather expensive and the largest extractor the writer has ever seen holds less than 400 grams and cost $10. It is also rather frail and if any part becomes broken the ent,ire apparatus is a loss. Description
wooden cover. A piece of blotting paper makes a good gasket for the contact between the ground-glass rim of the percolator and the wooden cover, and t,he cover is held in place by two quilting-frame clamps. Operation
Add the drug to the percolator in divided amount.s, moistening it well .with solvent. With dl connections tight, open the stopcock a t the bottom and allow sufficient solvent to flow out to about half fill the flask, pour in solvent through Two unusual pieces of glassware (Figure 1) are all that the condenser until there is a layer over the surface of the are required for the set-up under consideration. No. 1 drug, and then start the heating. When condensation is attached to the outlet at the bottom of an ordinary phar- commences open the s t o p maceutical cylindrical percolator by means of a perforated cock a t t h e bottom and cork as shown in the photograph. No. 2 is attached to an regulate the outflow to t~he upright condenser and the small tube passes through the same speed as t.he condensacover of the percolator. Nos. 1 and 2 are then connected tion. The process is then by a straight piece of glass tubing and rubber hose, or a continuous and unless there Liebig condenser as shown in the photograph. With a is leakage of solvent vapor or rariations in the heat B applied no further attention is required. Should the solution in the flask become too concentrated or if it is desired to remove i t at any time, close the stopcock, loosen the clamps on t.lie rod, and raise the entire apparatus holding it in the elevated position with the heavy clamp at the bottom. Disconnect the fla.sk, remove the contents, add to i the flask a new supply of solvent, return the entire apparatus to position, and continue the operation as before. If the solvent has a high boiling point, such as alcohol, the eondenser is required. Pass steam into this condenser at the top No. 1 No. 2 Figure I and out through thehottom. This keeps the tube hot and avoids undue eondensation in flask (a 250-cc. flask is ample for any size outfit) attached the tube and return of solvent to the flask by this route. to tube No. 1, the proper water connections and support The steam may be introduced from a laboratory supply or in place, and a heater, either steam bath or electric, the by boiling water in a flask as illustrated. For the other solapparatus is ready for operation. The size of t.lie percolator vents mentioned below the condenser is not required. is limited only by the distance between A and R of No. 1. The set-up has been used with a number of drugs find witli The percolator illustrated is 17 inches long and the maxi- ether, chloroform, carbon disulfide, petroleinn etber, and mum diameter is 3 inches. This percolator will hold about alcohol &s solvents, and in no case has there been difficulty 500 grams of ground diug. By making the distance from in operation. It is highly efficient; the writer has comA to B even an inch greater or by boring the hole in the pletely removed the oil from 500 grams of linseed meal in cover to one side of the center, a percolator having from 90 minutes. three to four times this capacity may be used. Modification without Lower Tube FThe percolator cover used by the writer consists of a circular piece of half-inch board with a hole bored in the Recently the lower tube, the most expensive and difficult center. The upper tube, No. 2, is fitted to a perforated to obtain, has been eliminated and in its place a straight cork and this cork in turn fitted tightly into the hole in the tube with a stopcock is used to connect the percolator with a Received November 19, 1926. the distilling flask and through a second larger perforation
I,VDUSTRIAL AND ENGINEERING CHEMISTRY
April, 1927
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in the cork of this flask is passed a half-inch tube bent to connect with the condenser tube. This greatly simplifies the apparatus, as anyone can bend this tube, and tubes with stopcocks are regularly marketed by any apparatus house. In so far as this modification has been used it has proved as satisfactory as that illustrated. In the writer’s opinion an extractor of this type could be constructed from metal such as copper, zinc, galvanized iron, etc., and made even more satisfactory than the one illustrated.
3-It does not siphon; therefore the entire drug is constantly in contact with the solvent. 4-The receiving flask may be small regardless of the amount of drug used or size of percolator. 5-Since b u t little more solvent is necessary than required to wet the drug, it is very economical of solvent. 6-The extraction can be stopped at any moment by closing the stopcock. ”-Since the drug is constantly bathed with solvent, no fissures form through which the solvent flows and therefore there is no danger of incomplete exhaustion.
Advantages of Apparatus
Acknowledgment is made to C. C. Glover, of the University of Michigan, for advice and encouragement during the progress of the work.
1-It is much cheaper than a Soxhlet of equal size. 2-Any part, if broken, can easily be replaced at small cost.
Acknowledgment
Automatic Devices for the Extraction of Powdered Materials’ By S. Palkin and H. R. Watkins DRUG CONTROL LABORATORY, BUREAUOB CHEMSTRY.WASHINGTON, D . C.
tinuous agitation of the susTwo automatic devices for the extraction of solid subpended mass by means of tionl4,*several automatic stances, particularly plant drugs, are described. One pressure from solvent vapors devices for the extraction is an inexpensive, simple device, in which the extracting characterize the second or of liquids by immiscible solsolvent is made to flow rapidly upwurd through the more complex form, V. vents were described. By a sample and is continuously filtered through a cotton The value of sending the simple modification the apfilter device back into the heating vessel. Absence of hot solvent upward through plication of one of these liquid a thimble and upward flow of solvent keeps the powthe mass, thereby keeping the extractors may be extended dered material loosely suspended. The circulation ma t e r i a 1 loosely suspended to the extraction of powdered principle causes the solvent to flow through the whole and permitting very rapid or other solid material. Anmass of sample evenly with no stagnant central cores, c i r c u l a t i o n of the solvent o t h e r a n d somewhat more as might be the case where a thimble is employed. throughout the mass, has long complex form is based on the The same extractor vessel or jacket may also be used for been r e a l i z e d . Practical principle of forcing solvent the liquid extractors previously described. difficulties of effecting convapors into the suspended The other device, somewhat more complex, makes mass to be extracted. tinuous filtration during exuse of the pressure effect of the solvent vapors to proThe literature c o n t a i n s traction exist, however. duce continuous agitation of the suspended sample. One of the simplest forms many articles on the forms of Continuous filtration is effected in the same way that extraction devices and comembodying the principle of it is in the simple form. This apparatus is applicable mercial catalogs show numerthe continuous upward curto the extraction of liquids as well. ous types of such apparatus rent is described by Budde2 actually available. In the for t h e extraction of wax. main, those now used for the extraction of solid material fall Several slight variations of this form are also noted.6J1s21 into two general classes: (a) those in which the fresh solvent The difficulties with this very simple form are not appardrops from the condenser into a reservoir containing the ent from the description. They manifest themselves in material enclosed in a thimble for extraction and periodically practical application. Whenever a charge to be extracted siphons back into the heated vessel, most of which may be is confined between two layers of filtering material such regarded as employing some modification of the Soxhlet as cotton and the extraction solvent is a t the boiling point, principle; (b) those which involve the continuous percolation a pocket of vapor forms between the sample and upper of hot solvent downward through the mass to be extracted, layer of filtering material. This prevents the passage of and may be regarded as similar in principle to the Knorr, solvent all the way down through the supply tube and Bailey, and Riley extraction apparatus. causes the freshly condensed solvent to spill over the top The extensive use of these solid extractors is evidence of of tube, thus diverting the solvent from penetration of the their value in analytical work. I n practically all cases a mass to be extracted. This is particularly true when ether thimble, usually paper or cloth, is necessary for carrying the is the extracting solvent. Free communication with the charge. The solvent is made to pass downward through the atmosphere or vapor directly above the solvent is essential mass. to uninterrupted circulation of solvent upward through the Passing a continuous current of solvent upward through the sample to be extracted. Filtration in our apparatus is acpowdered material to be extracted and eliminating the thimble complished by means of a simple vertical filtering partition. characterizes the simple form of extractor 8. This and con-
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N A previous p u b l i c a -
1 Presented under the title “Automatic Devices for the Extraction of Plant Drugs” before the Division of Chemistry of Medicinal Products at the 72nd Meeting of the American Chemical Society, Philadelphia, Pa., September 5 to 11, 1926. Numbers in text refer to the bibliography at end of article.
*
Type S Apparatus
Figure 1 shows the simple type, S. The jacket tube, A , is the same as that used for the extraction of liquids.’& Three other very simple and inexpensive pieces (aside from Erlen-
