March 15, 1933
INDUSTRIAL AND ENGINEERING CHEMISTRY
101
EFFICIENCIES OF Two DE-ALDEHYDINQ TABLEI. COMPARATIVE is actually a partial dehydration of the product, the moisture PROCEDURES content in this instance having been reduced from 7 to 3 OFFICIALMETHODPROPOSED METHOD TIME per cent. This, however, is less important than that the Mg./cc. Mg./cc. Min, proposed mode of procedure is efficient, economical of time 0 10 and materials, and simple. It has been put to test with 30 good success for the past year in the student laboratory of 40 60 the Department of Chemistry and has never failed to pro90 120 duce an excellent product when the conventional methods proved wanting. It :was, of course, inevitable that resinification of some Throughout this study all distillations, both reflux and of the aldehyde should occur in that portion to which both otherwise, were made in an all-glass apparatus (Figure 1) aluminum and alkali had been added; nevertheless it is which had been constructed from a round-bottomed flask, apparent that the reducing action.of the metal is a material a straight condenser, and a ground-glass joint, the latter aid in speeding up removal of the aldehyde. The evidence being given a reverse bend. By merely turning the conappears convincing that the last traces of aldehyde bodies denser from its upright position for reflux distillation through are removed with greater dispatch and convenience than by an angle of M O O , the system becomes a distillation outfit other procedures. It is these last traces which appear to without the necessity of interrupting the heating. be the troublesome factors in purifying ethyl alcohol for alkali-solvent purposes. ACKNOWLEDGMENT As a result of a series of determinations of saponification Acknowledgment is made of the assistance given by Milford numbers of fatty oils with reagents prepared from ethyl alcohol, purified on the one hand by the silver oxide method A. Cowley, who helped design and construct the all-glass (4) and on the other by the combined action of alkali and apparatus used. metallic aluminum, it was found that the use of ethyl alcoLITERATURE CITED hol treated by the latter procedure causes no significant (1) Assoc. Official Agr. Chem., Official and Tentative Methods, p. differences. Pertinent data are recorded in Table 11. TABLE11. COMPARISON OF SAPONIFICATION NUMBERS OIL Sesame Cottonseed Rye ~
~~
ALCOHOL ALCOHOL BY SILVPR ALUMINUM AND OXIDP POTASSIUM HYDROXIDE
BY
191.8 194.9
176.5
191.6 196.0 176.8
A rough determination of the water content of a sample of alcohol before and after purification has shown that there
144 (1930). (2) Ibid.. D. 256.
(3j Chade; E. M., J. Am. Chem. Soc., 28,1472-6 (1906). (4) Dunlap, F. L., Ibid., 28,395-8 (1906). (5) Englis, D. T., and Mills, V. C., J. Assoc. Oficial Agr. Chem., 12, 248-50 (1929). (6) m'inkler, L. W., Ber., 38, 3612-16 (1905). RECEIV~ September D 2,1932. Presented before the Division of Agricultural and Food Chemistry a t the 84th Meeting of the American Chemical Society, Denver, Colo., August 22 to 26, 1932.
A Laboratory Esterifying and Fractionating Apparatus CARROLA. DORAN, E. I. du P o n t de Nemours & Co., Inc., Research Laboratories, Parlin, N. J.
T
HE difficulty of duplicating exact plant conditions of large scale processes in smaller laboratory equipment is well known in industrial research laboratories. In plant distillation processes the equipment used is usually capable of being operated over a very wide range of conditions. These variations include rates of operation, amounts of reflux, ratios between internal and external reflux, points a t which reflux is returned to the system, points of crude feed to the system, selectivity in layer take off in the condensate, etc. Many types of laboratory columns (1, 2) and distillation set-ups (3, 4,6) have been described in the literature for bringing about careful, precise fractionations. The use of such equipment is primarily for analyses by fractionation and cannot readily be applied t o the duplication of general plant procedure The apparatus here described has been successfully used in the research laboratories of the du Pont company in connection with the manufacture of industrid solvents, plasticizers, etc., involving plant problems dealing with fractionation, vapor drying, and liquid-vapor countercurrent flow. As shown in the accompanying figure, it is fitted with a vapor line from the kettle, as well as a separate liquid reflux line
to the kettle. The fractionating portion of the column is large to give capacity to the apparatus and is fitted with side auxiliary taps to provide various feed points, thermometer wells, or reflux return points along the column. The dephlegmator is adjustable in the cooling-water height as well as rate of cooliiig-water flow. The receiver is suited to take off either layer of a two-layer condensate and to return either layer part,ially or wholly to the kettle or to various points in the fractionating column. The fractionating portion of the column is well insulated to prevent the transfer of heat from the liquid and vapors in the column to the outside wall. This minimization of heat transfer from the column is very important in duplicating plant conditions where the transfer is very small. Experience with this apparatus has shown it closely to approach plant duplication. DESCRIPTION, ASSEMBLY, AND OPERATION The over-all height of the apparatus as shown in the figure is approximately 111 cm. (44 inches) and it occupies about 0.09 square meter (1 square foot) of bench space. It is assembled from three major parts: kettle, column, and re-
102
ANALYTICAL EDITION
c e i v e r . All t h r e e c a n be made of P y r e x glass. The column is 1a g g e d by wrapp i n g t i g h t l y first, w i t h asbestos rope and then with tape to add c o m p a c t n e s s and d u r a b i l i t y to the insulation. 1 indicates the portion of the column l a g g e d . T h e d e p h l e g m a t o r A is made by boring and cutting a No. 9 rubber stopper, as shown in the small inset N The small holes are for water inlet and outlet lines. The upper stopper is cut in the same way except that o n l y one small h o l e i s n e e d e d , which acts as an air passage. A strip of m e d i u m t h i c k p y r o x y l i n s h e e t i n g is cut 12.5 cm. (5 inches) wide and a b o u t 20 c m . (8 i n c h e s ) long. This is rolled to approximately the size of the dephlegmator, t i e d i n t h i s p o s i t i o n with s t r i n g , and placed in an oven a t 90" C. for one hour. Upon cooling and untying it will be found to have assumed the rolled form. The rubber stoppers are then put in place on the FIGURE1. ASSEMBLED column and the slits closed APPAFLATUS by drawing fine wire around A . Dephlegmator the stopper a t two or three B. Condensers C. Sorcw clamp points. The pyroxylin roll D. Sliding HzO cutlet is then put in place around E. Liquid trap F. Separating receiver the stoppers and sealed by H. Fractionating mediu.m I. Lag ing pouring acetone between the J. s o d stops o v e r l a p p i n g surfaces a n d K. Kettle L. Three-way stopcock holding tightly in place for M. Auxiliary taps N. Lower stopper for depkilega few s e c o n d s , T h e pymator roxylin shell will seal itself P. Receiver showing siphon for returninz lower laver t o firmly. F u r t h e r to insure oolumn tightness and strength to the dephlegmator all joints are covered with a generous coating of du Pont household cement. The water inlet and outlet are formed of glass tubing, as indicated in the drawing. The outlet tube, although it must fit water-tight, should be loose enough to permit it to slide up and down through the rubber stopper, as this is an adjustable feature of the dephlegmator. The upper condenser is constructed in the same manner as the dephlegmator, except that the upper rubber stopper does not have an air-vent hole and the stoppers do not need to be slit, as they can be moved into position over the arm of the column. The lower condenser may be fitted with a glass shell which is slipped with the rubber stoppers over the end of the column arm. The water inlet is through the lower stopper, while the outlet is through the upper stopper. The condensers should be constructed to cover as much of the column side arm as possible. The assembly of the dephlegmator and upper condenser may be greatly simplified by having the column made with a ground-glass joint in the small part of the column and another in the horizontal section of the side arm. This will, of course, increase the cost of the column. A still further improvement with additional expense would be to have
Vol. 5 , No. 2
condensers blown on the side arm during the manufacture of the column. Having assembled the dephlegmator and condensers, the column is filled with a fractionating medium, such as glass beads or coarse Carborundum, to the point where the restriction in its larger diameter begins. Care must be taken not to fill the column too full, as an obstacle in the smaller upper section will cause flooding and greatly decrease the capacity of the column. The glass receiver is connected with the column, as shown in the figure, through the liquid trap E. The trap is made of O.1G-cm. (0.06-inch) capillary glass tube with an outer diameter of 0.63 cm. (0.25 inch). Such a trap is strong and will not retain appreciable liquid The various connections of rubber tubing, shown in the figure, are made to complete the assembly of the apparatus. It should be noted that the condenser outlet fits loosely in the receiver, so that pressure does not build up in the apparatus during operation. I n operating the still as a drying column, the receiver is set so that the separating chamber will fill with the condensate. When the chamber is full, the oil, or water carrier; will flow through the return line either to the column or directly to the kettle, depending on the setting of the threeway stopcock L. The water settling out in the separating chamber may be drawn off through the bottom as it collects. If the water carrier used should be a liquid heavier than water and forms a lower layer, the siphon shown in the inset P may be used. It consists of a small-bore Lshaped glass tube with a short piece of rubber tubing attached, and is placed in the receiver as illustrated. The piece of rubber tubing should be of a size to fit snugly, but not tightly, in the upper return line of the separating receiver. The siphon is primed by allowing the receiver to fill beyond the upper outlet. After once started it will maintain a definite upper level in the receiver and will remove only the lower layer. The internal reflux or dephlegmation of the column may be regulated by regulating the amount of cooling water flow through the dephlegmator as well as the height of cooling water maintained in the dephlegmator. The screw pinch clamp C adjusts the flow of cooling water, while any desired height of cooling water in the dephlegmator may be obtained by the proper setting of the sliding outlet D.
SUMMARY The distillation apparatus described is extremely versatile in its application. It is designed primarily to duplicate in the laboratory the conditions of large plant stills used in esterification, rectification, and drying processes as carried out in the chemical industries. It is of simple construction, easily operated, requires very little space, and is suited to work with practically all commercial solvents. ACKNOWLEDGMENT The writer wishes to thank J. R. Buckley, T. J. McKeon, T. Hill, J. P. Burke, H. W. Durrua, and C. Pyle for their contributions in the development of this apparatus. LITERATURE CITED (1) Clarke, H. T., and Rahrs, E. J., IND. ENG.C H m f , 18.1092 (1926). (2) Ibid., 15, 349 (b923). (3) Leslie, E. H., and Geniesse, J. C., Ibid., 18, 690 (1926). (4) Marshall, M. J., I b i d . , 20, 1379 (1928). (5) Peters, W. A,, and Baker, T., Ibid., 18, 69 (1926). RIOCEIYBD September 22, 1932.
