Versatile Transfer Technique In the course of our investigations, we required a convenient means to transfer air- and moisture-sensitive substances from one Schlenk apparatus to another. Use of a long, double-headed needle (e.g., a so-called "cannula") extending between the two vessels is standard for such a task. However, two complications arise with this procedure. First, how can one maintain aslow and constant flow during the transfer? Since reagentsare added to our Schlenkware via a syringe attached to a syringe pump (Sage Instruments, Inc., Model 341AL it would be particularly efficient to adopt the same device for the transfer oneration. Toaccomnlish this. after one inserts thecannula to connect the twovessels. a 30or50.mL lightly greasedsyringe, pre-filled withan mert atmosphere, isclipped onto the syringe pump. Attached to theend ofthesyringe isashurt length (-12in.j of heavy-walltd,',-in. plastic hose, which, in turn, isattached tothestopcorkofthe Srhlenk tube. As the syringe pumpdrivesin the barrel oithes)ringe, inert gas i* injected into the Schlenk apparatus at a rate commensurate with that of liquid transfer through the cannula. Using the syringe pump, transfer times for solution delivery are reproducible within approximately 5%.To date, the only problems we have noted are that it is essential to use nonviscous solutions and that suspensions tend to clog the cannula. Second, how can one effectively cool a larger-sized (e.g., 250-mL) Schlenk apparatus? We have found that one can construct a VeN inexnensive d m icelacetone cooline bath from a discarded nlastic container (those su~nliedbv Fisher of Celite 1 ~ e z ; s t e~~~-~ r e d ~ r a d e ~ a,r~kil l & id (Cat. No. ~ 2 1 .1area& ) suit&le).an Scientific. Ine. Eor their ~-~~300-eo&kae& "~~~ 800-mLbeaker, and sufficient vermiculite tu fill thr plastic conraincr -7090 full. 7.h; &ss beaker r~ then wedged inrothe spongy vermiculite with constant turning until a fairly wen layer of insulntion hap heen dxained. As an added bonus, the beaker is held snugly by the vermiculite, thereby allowing one to dispense with the traditional wax overlayer. With this bath, it is possible to cool simultaneously nearly three-quarters of the Schlenk tube's surface ~~
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J. I.. Belletire, D. F. Fry, and C. Hagedwn
University of Cincinnati Cincinnati, OH 45221
Volume 65
Number 10
October 1988
913
