Sideways Stirring
'ip-"l
n
\%en a vrsarl containing n soluuon can he pusitionrd on n makmttrc stirring plate, n atirhar provides s irmple mcthnd tostir the snlut~on.This trchn~quecanb r e u t m d ~ d to situiltlms in which the botrorn i d the flask l a inaorr;s~blr ibr, rxomple, a rrnetion
flask partially submerged in a large controlled-temperature bath. AS-shown in the figure, a stirring bar can he driven by means of a stirring plate mounted to one side of the flask. The center line of the stirring plate must be placed above (or below) the plane ofthe magnetic bar. In this way the magnetic flux from the stirrer sweeps past one side of the stir bar. sttractineone .. end and reoelline the other. This method works best with round-buttomrd flaskithntarrplncedntxttothrst~rrrrusingslnu.nrrnrd~uniip~nn~ng dpc~d.;,but the m a m t t w bar g r n e r a l l ~ p e into s chamcrnotlon in large. flat-bottomed containers. One solution to this ~ r o h l e mis to use a mametic bar with a commercially available peripheral ring (finned or smooth) placed around it.' More demanding conditions require the use of a n overhead stirring motar, shaft, and stirring blade, or other more elaborate stirrers.2 ~~~
/
~
.
-
'Available from most large laboratory supply houses, such a s Baxter Scientific Products, Baxter Healthcare Corporations, Scientific Products Division, 1430 Waukegan Road, McGaw Park, IL 60085-6787. 'Grinstead, J. H.. Jr. and Sullivan, J. M. J. Chem. Educ. 1990, 67, 521.
Griffith Liang Northwestern University Evansfon, IL 60208-31 13
Volume 68
Number 6
June 1991
525
