Richard 0. Carleton
Radioisotope Service Veterans Administration Hospital Minneapolis, Minnesota
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Rotating- Vacuum Evaporator
The rod is attached to an adjustable arm extending out A n all-glass rotating vacuum evaporator from the mounting panel. for the rapid, bump-free volume reduction of liquids has A geared motor3 with a shaft in the motor axis drives been particularly useful in organic syntheses and for the spindle by means of a plastic belt which fits around preparing biological extracts for analyses. Important the motor pulley and the metal sleeve through which the features not usually found in commercially available spindle passes. The pulley diameters are 211/16-in.for units are fast rotation, freedom from sample contamithe motor pulley and ll'/&n. for the metal sleeve. nation by metal corrosion, easy adjustment and cleaning Belt tension is easily changed by the adjustable motor of component parts, and a water-jacket condenser. mounting. The heavy-walled glass connecting spindle has a The complete assembly is mounted on an L-shaped 24/40 tapered male joint at one end and a 28/12 socket panel which pivots on a horizontal rod a t the top of an joint a t the other end. A round-bottom flask with a upright support. The evaporator is fixed at any desired 24/40 tapered female joint containing the liquid sample angle of inclination by a knurled nut which is attached to be evaporated is placed on its complement joint of the to the panel and tightens onto a rod which pivots from a spindle with no lubrication. The spindle extends point on the upright support. through a metal sleeve which rotates on two ball bearings by a belt drive from the motor. Eight set screws mounted in the sleeve bear against a fibre bushing and plastic-coated tape which immediately surround the spindle and cause the spindle and sample flask to rotate with the metal sleeve.' The set screws also function to center the spindle in the sleeve. The vacuum takeoff consists of a 28/12 glass ball joint followed by a 90-degree bend and a short water-jacketed condenser with a hose connection a t the end of the condenser. The hose leads to a trap and a water pump. A 3-mm stopcock joins the takeoff at t,he 90-degree bend and is oriented approximately in the axis of the spindle. The takeoff is supported by its 28/12 ball joint resting in the rotating 28/12 socket joint of the spindle and by a #€I rubber stopper which fits over the end of the condenser. The stopper is held by an adjustable clamp. This method of support holds the takeoff firmly, yet allows the takeoff to accomodate itself to slightly off-center spindles and permits easy disassembly of the ball and socket joint for l~hrication.~ Depressions are cut into the ball joint to provide a Rotating vacuum evaporator; A, gromd toper joint 24/40; 8 , rotating reservoir of lubricant. metal sleeve and glass connecting spindle; C, boll ond locket ioint 28/12; D, water iacket condenser; E, rubber stopper support for vacuum takeoff; The water condenser accelerates the evaporation of and F, switch and copocitor. some liquids and, when desired, facilitates the collection of the resulting condensate. The condenser can be The sample flask rotates a t approximately 250 rpm eliminated from the vacuum takeoff, however, and the with light loads and at slower speed with heavy loads. design is then simpler, being but a 28/12 ball joint, a These revolving speeds are essential for the controlled 90-dcgree bend in the joint tubing, and a hose fitting p!us evaporation of liquids which have low boiling points, a 3-mm stopcock at the 90-degree bend. This abbresuch as ether, acetone, ethyl acetate, and chloroform. viated takeoff is supported by its hall joint resting in the Relatively high rates of rotation are especially necessary rotating socket joint of the spindle and by a rnbberwhen these low boiling liqnids are evaporated in small covered metal rod which passes through a glass tunnel flasks to induce the required turbulence in the sample in the center of the takeoff at a right angle to the axis. despite the small circumference of such flasks. The system, operating under the reduced pressures of 1 Metal sleeve, together with hearings and fibre bushing, purchased from Frederick Sellmer. 80 East 236th St., New York 70, N. Y. Lubriseal, purchased from Arthur H. Thomas Co., Philadelphia, Pa.
256 1 Journal of Chemical Education
Motor, induction 2-pale, 142-rpm output speed, Model 10072 IN, purchased from Borg Equipment Division, Amphenol-Borg Electronics Corp., Janesville, Wia.
a water aspirator, can be rapidly equilibrated with the atmosphere if a sample foams excessively by manipulation of the stopcock a t the takeoff. The slightly offset position of this stopcock splits the incoming airflow in a manner to prevent condensate and other extraneous matter in the hose and trap from backing into the sample. Dry air may be admitted to the evacuated system by attaching a desiccant column to the stopcock.
To hasten evaporation of high-boiling.point liquids and to prevent the accumulation of frost on the outside of the flask when a low-boiling-point liquid is being rapidly evaporated, an infrared lamp or a warm water bath may be used to apply heat to the rotating sample flask. The assistance of John Erickson in the fabrication of this apparatus is acknowledged.
Volume
39, Number 5, May 1962
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257
