J. F. Hinton, A. Than, and E. 5. Amis University of Arkansas Fayetteville 72701
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An Automatic Distillation Apparatus
Often when large amounts of relatively pure liquids are being distilled, only the middle fraction is collected. Such distillations require a long period of time, so it is most convenient to use an automatic apparatus that collects and separates the first and second fractions and then automatically stops the distillation. We report here an easily constructed automatic device that meets these requirements. The features of the system are shown in the figure. The liquid fractions are collected and separated by a floating plug assembly, A. This plug, the tapered end of a No. 9 polyethylene flask stopper, is positioned inside 11-mm tubing by three small "Vigreux column" indentations. This allows the liquid to flow past the plug and into the first receiver, E. The liquid in the column, B, is removed by gravity flow action. The gravity flow section, D, is constructed from large capillary tubing. After the first fraction is collected, the liquid backs up into the column, B, causing the plug, A , to be pushed into the smaller 10-mm tubing, C, thereby closing this section of the apparatus to the subsequent distillate. Depending upon the initial volume of liquid to be distilled and the hold-up volume of the distillation column, the volume of the fractions to be collected is determined by the volumes of flasks E and F. Flask F, which contains the desired distillate, is connected to a U-tube, G, containingmercury and two lead wires. The wires are connected to a Sargent electrical relay unit, H, which is connected in turn to the powerstat, I, that controls the heating mantle. To prevent premature contact of the two lead wires, one of them is placed inside a piece of small diameter glass tubing. When flask F has been filled, liquid flows into the U-
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Journal of Chemical Education
tube, causing an upward displacement of mercury in the left side. An electrical circuit within the relay unit is then completed, thereby shutting off the heating mantle and automatically stopping the distillation. The U-tube is fitted with a stopcock so that after the distillation the liquid within the U-tube may be removed. The apparatus is also fitted with drying tubes, J. While this apparatus has been used for the distill* tion of rather large quantities of liquids, it may also be adapted just as well to the distillation of smaller quantities by decreasing the size of the plug assembly ( A , B, C, D)and receiving flasks. We wish to acknowledge the financial support by the United State Atomic Energy Commission Contract Number AT-(4Ck1)2069.
Automatic distillotian device lree text for identification of parh).
