INDUSTRIAL AND ENGINEERING CHEMISTRY
466
ity-moisture content curves is the difficulty of exactly measuring the moisture content of a large number of materials. Table I1 shows the results obtained experimentally with saturated salt solution of known water vapor pressure. SUMMARY
A simple, easily made manometric apparatus allows rapid measurement of equilibrium humidity: Operation is based on the measurement of pressure exerted before and after freezing out moisture vapor, thus avoiding error due t o adsorbed gases. Three fugacity curves for the moisture contained in natural products are presented.
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Vol. 17, No. 7
LITERATURE CITED
(1) Adama, J. R., and Merz, A. R., IND.ENG. CHEM.,21, 305-7 (1929). (2) Dunmore, F. W., J . Research Natl. Bur. Standards, 23, 701-14 (1939); Research Paper 1265. (3) Evans, R. N., and Davenport, J. E., IND.ENG.CHEM.,ANAL. ED.,14, 732-3 (1942). (4) Graebner, W. H., Am. Management Assoc., Packaging Series 11, p. 11 (1944). ( 5 ) International Critical Tables, Vol. I, p. 67, New York, McGraw-Hill Book Co., 1926. (6) Makower, B., and Dehority, G. L., IND. EKG. CHEM.,35, 193 (1943). (7) Yee, J. Y . ,IND. ENG.CHEX.,ANAL. ED., 16, 367 (1944).
Rapid Laboratory Evaporator K. S. KEMMERER M e a d Johnson & Company, Evansville, Ind.
T IS often necessary to concentrate or recover volumes of
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liquid in the laboratory that are too small for pilot-plant e q u i p ment but large enough to be very tedious with the usual Iaboratory distillation apparatus. The evaporator described is designed to hasten these operations. Dimensions may be varied to suit individual needs @). The apparatus is readily assembled from ordinary laboratory glassware except for the condenser (Figure 1). The condenser, D , made from 16-gage sheet copper, is 60 cm. long and 12 cm, in diameter, and is provided with two cooling surfaces as shown. Water is sprayed on the inner surface, thus giving a rapid flow of cooling water through this part of the shell. Water inlet (9.5mm.) and outlet (19-mm.) tubes may be of any desired size but should be large enough to permit a rapid flow of water. The heating tubes, A , are made much like an ordinary condenser. The inner tube is 27 mm. in inside diameter. The jacket is 50 cm. long and contains three openings. The bottom outlet is the condensate drain. The top outlet is connected t o a pressure gage and a safety valve adjusted to release a t 2 kg. (5 Ib.) pressure. I t is well to provide an air vent from this outlet by inserting a T-tube with one arm of the T partially clamped off. Steam is introduced through the third opening. The evaporator flask, B, is made from a 5-liter round-bottomed
WATER OUTLET
flask, which has a side opening placed slightly below the center of the flask and to the back. This position causes the entering liquid to swirl rapidly about the flask and thus aids in the evolution of the vapor from the heated liquid. The connection between evaporator B and condenser D is 30-mm. outsid, diameter tubing. The bottom drain is fitted with a stainless steel baffle late. The baffle is introduced through the neck of flask B wit{ the spring attached t o the lower end. The other end of the spring is hooked over the end of the drain tube. The baffle slows the spinning liquid sufficiently t o keep the drain tube full. Reservoir C i s made from a 1-liter round-bottomed flask. The receiver, E, is a 22-liter flask. The tube draining the condensate from the condenser is 15 mm. in inside diameter, giving adequate space for draining the condensate and maintaining the vacuum throughout the apparatus. All connections are made with rubber tubing and stoppers. The operation of the evaporator is simple. A single water aspirator is used as a means of reducing the pressure in the apparatus. The liquid is fed into the still until the level is slightly above the baffle plate in B. Steam is turned on in the heating tubes, A , using 1 t o 2 kg. (3 to 5 lb.) pressure. The heated liquid rises and circulates into B where the vapor is released. The remaining liquid circulates back through C t o A where i t is reheated. The raw liquid is fed continuously t o the still and the concentrate may be drawn off continuously a t F by connecting the concentrate outlet t o a flask maintained under a higher vacuum. Aqueous solutions are concentrated a t a rate of 10 t o 12 liters per hour under a vacuum of 25 mm. measured over receiver E and a temperature of 40 O to 50" C. Acetone distills at a rate of 35 t o 40 liters per hour under a vacuum of 250 mm., 70% alcohol distills at a rate of 30 to 35 liters per hour under similar conditions. For solvent recovery it is necessary t o use an additional condenser and receiving flask in the vacuum line. A block-tin coil surrounded by ice serves very well. Mitchell (I) has compared the over-all heat transfer factor for the evaporator here described with one of his own design and obtained values of 143 and 140, respectively.
8 pop VALVE
LITERATURE CITED
S T E M INLET
ER INLET
(1) Mitchell. D. T., private communication, 1945. (2) Mitchell, D. T., Shildneck, P., and Dustin, J., IND.ENQ.CHEM., ANAL.ED.,16,754 (1944).
CONDENSATE
Collective Index Reprinted UOUID INLET"
Figure I .
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Diagram of Evaporator
The first edition of 4000 copies of the Fifteen-Year Collective Index of the ANALYTICAL EDITION has been sold out, testifying to its value and the favorable reception that it is meeting. A limited number of additional copies are now being printed. Those who have not yet purchased the index and are interested in having it available for reference are advised t o place orders at once with the AMERICAN CHEMICAL SOCIETY, 1155 Sixteenth St., N. W., Washington 6, D.C. Send check with order-$2.25 per copy.
