Blowing up Balloons and Trash Bags in a Glove Box Most rrsearch g-mnpi using n ylmr LILX rou~lnrlyh a w P . ~ tc I clmn,~c.lht' xmuiplww ~ n i d itc romplrrrly. Thl? con be ~ I I to P art accident that cxposei the box to s v p ~ l i e n n ts r n w n t i ofmr i,r 10 rlcnnang. Shn\.r,rand I)rrrdzm1 dtarr~hr two limiting cases for replacement of the atmosphere in the glove box by inert gas. 1.The incoming gas ~ u s h e out s the air in the glove box with no mixing. In this case only one volume of inert gas is needed to purge the bo;. 2. The incoming gas mixes completely with the air in the glove box. Removal of air is much slower in this case. The fraction of air remaining after n volumes of gas have been used is then e4.
In the second case, the authors estimate that 10 volumes of inert gas are necessary to reduce the air content to 45 ppm.2Actual purging efficiencies usually lie somewhere between these two limits, and P I 0 gas volumes are necessary to achieve a good purge. Due to the time and expense of these purges we sought a way to reduce both. A first approach was to fill balloons3 in the glove box with inert gas. As the balloons are filled, the air in the box is pushed out through an exit bubbler or evacuated using a vacuum pump. While this leads t o a festive atmosphere, balloons do not pack as well as trash bags.' The free air in the glove box can be reduced to 75-90% in the first filling. The residual 10-2516 air is then purged as described in the literature' using roughly one volume of gas. Finally, the closed trash bags are taken out of the glove box through the antechamber one a t a time. The trash hags are not opened in the box since they may be contaminated with air either through slow dimusion or when they were closed and tied. This requires a third volume of gas and results in further purging of the atmosphere. We have found that use of three volumes of gas in this way leads to an excellent reproducible initial purge of the glove box. 'Shriver, D. F.; Drezdzon, M. A. The Manipulation of Air Sensitive Compounds, 2nd ed.; Wiley: New York. 1986.
'~heseresidual levels are normally reduced further by use of recirculating purification systems. Due to the low capacity of such systems it is desireable to reduce as much a s possible the amount of residual air. 3"~elium-quality" balloons are available at low cost at party supply and toy stores. 'we have found the Hefty brand Cinch-Sack, to be particulary convenient. Gerald C. Roper Dickinson College Carlisle, PA 17013 Gabor Kiss, Shakti L. Mukerlee, and Carl D. HOW Univeristy of Miami Coral Gables, FL 33124
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508 '
Journal of Chemical Education
