The Construction of an Inexpensive Rotary Evaporator
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The utilirntion of rotarv, evamrators in undereraduate oreanic lahoratorv has several advantaees. Since solvent re~~-~~~ mwnl I.. oricn the "rare limiriny"step in many experiments. onlv a minimal number of surh proredllr~sCan he Inrurpn. . hlnnv paperrmenu such as multistrp synrhrsr.. and rolumn ehrnmntograph~creparamwd in n smrle l a h o r a t ~ )prriod. r ~ m nrc s thus reitrirled and uften mrercstinr: rracthmi can nor be donr dur to solvenr removal d ~ f f ~ r u l t Also ~ r s . mmhlc are the superior safety aspects of rotary evaporatprs in that volatile solvents can be trapped efficiently in an ice coaled receiver. Fire and inhalation danger is thus significantly reduced. A major drawback to the use of rotary evaporators is their cost. The simplest all Teflon-glass model, much preferable to a metal surfaced model, costs upwards of $200 (complete setups are often more than $300). A rotary evaporator which is rugged, simple, and inexpensive can be constructed in the following fashion. Three parts must be purchased: a motor, Holtzer Cabot Model RBC 2510 60 RPM motor, $17.95; s bearing, Fafnir ER-16 Bearing GCIlOKRRG2, $6.14; and a Teflon rod, 1 in. dia X 6 in. length, $6; The motor is an unused hut removed from equipment item from American Design Components, 39 Lispenard St., New York, N.Y., 10013 (other geared motors of 30 in.-oz of torque or more could he used also). The hearing can be purchased locally a t hearing shops and the Teflon rod is usually available locally through glass shops. ~~~
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_FJ Figure 1. Schematic of
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unH Figure 2. Assembled apparatus.
The unit is assembled as in Figure 1. The motor (A) is mounted on a piece of %-in. aluminum plate (3% in. X 6 in.) (fl) and the motor shaft protrudes through the plate. Two pulleys must be machined from aluminum. The first (C), which is 2% in. in diameter, is affixed to the motor shaft, and the second (Dl, which is 1%in. in diameter, is affixed by set screws to the Teflon rod. The Teflon rod ( E ) ,which is drilled lengthwise with a %-in. hole is placed in the hearing (F) and seated with set screws. The hearing, which has an outside diameter of 1%in. is placed in e hole of this size in the aluminum plate and held in position by set screws. This arrangement permits the Teflon rod to he supported by the bearing and turned by the pulleys using an O-ring belt. One end of the Teflon rod is turned to 2%o 3 joint dimensions and the other end, which g m ; to the cmdenser and receiver, is turned to s ':, convex spher~caljolnt. A condenser having a a m r n v r 3,spherwal pint at the tdp of an angle of XI0 is clamped vertrcally {Kg. 21. The motor unit is clamped inro posirim hv a sumcm rod t O I screwed to the top uf the almninmn plnrc ~ f land ) ra tilted 20° to meet the luint of the conden.;. er. he ~ e f l o nt o glass rotating joint is luhiicated with stopcock grease. A vacuum flask a t the lowe; end of the eondenser which provides the vacuum attachment completes the apparatus. Alternate condensing systems such as Dewar condenser. cnn . he used if desired. U h g a ligure of $45 iur lahor and $30 for the glassware and condenser giwa a complete rotary evaporator setup for h95.The draight through design permm eaq rleanmg and the unit is able lo withitand student cab-,use well. ~~
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New Mexioo State University L a s Cruces. 88003
R. V. Hoffman
Volume 53.Number 7,July 1976 / 459
