472
INDUSTRIAL AND ENGINEERING CHEMISTRY
It may be of theoretical interest to indicate the reasons why a uniform rate is maintained despite vacuum and air pressure conditions in various parts of the system. The air space above the liquid in the Mariotte bottle reservoir is under vacuum equivalent to the hydrostatic head between the surface of the liquid on the one hand, and the end of the air tubc, b, on the other hand. If liquid were to be added directly through a tube and funnel, without the use of a vacuum pump, the air would be compressed and no air would be drawn in through b; accordingly, equilibrium conditions would be disturbed. However, if during refilling a vacuum pump is attached to the air space of the reservoir, as indicated in Figures 2 and 3, the volume of air drawn out of the bottle will be greater than the volume of liquid drawn in, any difference being amply taken care of by the air intake through
Vol. 16, No. 7
be inserted between the end of the glass tube, f, and the rubber hose, d . When heavy suspensions, on the other hand, are to be handled, all tubes and tubing should be as wide as possible, with hydrostatic head, H . kept correspondingly low. These deviccs have all been in active operation in conjunction with small-scale continuous water-softening tests and in studying particle size distribution on diluted oil-well-drilling muds. ACKNOWLEDGMENT
The help of George H. Fancher of the University of Texas is gratefully acknowledged in many phases of this work
b.
LITERATURE CITED
If the liquid used is suspected of containing suspended material that may clog the orifice, a filter (such a8 a glass wool plug) map
A
(1)
Page and Whitwell. IND. ENG. CHEM..ANAL. ED.,15, 13.5-7 (19433)
Large-Capacity Continuous Solids Extractor N O R M A N APPLEZWEIG, Debruillr Chemical Corp., New York, N. Y.
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F T H E innumerable designs which have been published for glass extraction apparatus (6),very few are adaptable to large-scale work because of their expensive and unwieldy construction. Large-capacity extractors of simple design have been described by Beal (f), Drake and Spies @), Smallwood (6),and Jonnard (4). While these can all be made from standard Iaboratory glassware, they suffer minor disadvantages which limit their usefulness The apparatus described below has been designed to overcome these disadvantages. It can be constructed from standard, readily available glassware in sizes up to 22 litera. It can be charged and emptied without dismantling. The size of the extraction chamber is not limited by the size of the solvent flask. Provision is made for taking off samples without interrupting the extraction. The extraction is accomplished efficiently.
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The basic constituents of the extractor are a glass bottle, a condenser, and a flask. The extraction chamber is made from un inverted Pyrex bottle, A , by cutting off the bottom and grinding the rim to fit smoothly to a ground-glass plate which acts as a cover, B. A hole is drilled in the side of the bottle 2 to 3 cm. below the cover and a tubulature is welded on a t C . (An aspirator bottle with tubulature may be used if available in the desired size.) The solvent is vaporized in the flask, E , and condensed by the condenser, from which it flows through F into the extraction chamber. The extract returns to the flask by means of a glms tube which is inserted through a cork, D, a t the bottom of the extraction chamber and bent so that when the extraction chamber is filled, the condensation of additional solvent will cause an overflow back t o the flask. The connection a t F may be made by semiball joints or by Thiokol tubing. If desired, the corks at C and D may be replaced by all-glass joints. Samples may be taken off from time to time by means of a stopcock a t D. CHARGING.The extractor is charged by removing the groundglass plate cover, B, and placing a bag containing the material to be extracted on the perforated porcelain plate, I. The extraction chamber is filled with solvent and then a sufficient excesa is added so that the overflow fills the flask to a desired height. The cover is replaced and the extractor is ready for operation. EXTFLACTION. The flask is heated and the condensed solvent enters the extraction chamber, displacing the extract through the return tube back into the flask. The material is extracted by constant percolation and soaking instead of repeated exhaustion as in the Soxhlet apparatus. This method of continuous removal of the solvent from the bottom of the extractor at the same rate that fresh solvent enters the top has been shown to be decidedly more efficient than the Soxhlet exhaustion method (3). Furthermore, the volume of the flask is limited'only by the rate at which one wishes to distill and the flask does not have to be lar e enough to receive the entire contents of the extraction cham%er as in the Soxhlet type of apparatus. Thus a relativelv small amount of solvent may be heated a t one time. To enipty the extraction chamber, the residual solvent is withdrawn through the stopcock at D and the Rpent charge is removed through the top. LITERATURE CITED (1) B e d , G. D., Org. Syntheses, Coll. Vol. I, p, 539, New York, John Wiley & Sons Co., 1941. (2) Drake and Spies, IND.ENO.CHEM.,ANAL.ED.,5,284 (1933). (3) Faith, Peterson, and Smutz,FoodIluluslries, 13 43 (1941). (4) Jonnard, R., IND.ENQ.CHEM.,ANAL.ED., 16, 61 (1944). (5) Morton, A. A , . "Laboratory Technique in Organic Chemistry",
New York, McGraw-Hill Book Co., 1938. ( 6 ) SmsUwood, E., IND.ENG.CHEM., ANAL.ED.,14, 903 (1942)
