A Convenient and Improved Technique To Reduce Substantially the Problem of "Bumping" While Using a Rotary Evaporator
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Todav. .. everv modern chemistrv laboratorv. is eauivoed . .. with a rntarv nerfarms raoid wanoration of solvents from ~wanorator . ~ , that~, reaction mixture^. However, f o a m m ~01t h r solvent sommmes occurs, resulting in a process that chemirtr rall "humping". Loss of product is often the unfortunate consequence. In addition, the rotary evaporator must be cleaned, a procedure that can be time-cons w i n g . To help to avoid these pitfalls, scientific product companies offer different types of traps. We would like to introduce a very simple type of laboratory eauinment that does not trao the eomwunds but that oerforms better than commercially available rotary evaporator tram by keeping as much of the reaction mixture aa posaihle frum escaping from the flask. This device is nothing more than a "normal" connecting adapter that expands the length of alaboratory apparatus or is sometimes used as an air condenser. Combined with a fritted funnel, which is normally utilized for direct filtration (see figure), it can be used to minimize the oroblem of humnine. The arts for making this device (fritted tube and connecting adapter) are available from many aeience product companies. The actual process of combining these two pieces is avery simple procedure for anyglass blower. The actual cost for thefritted adapter is about half of the amount one would pay for a "normal" rotary evaporator trap. The fritted adapter works as follows: after the solvent "bumps", the content of the flask will rise through the adapter until it reaches the fritted material. Only a small amount of solvent will be able to pass through the frit. The force exerted by the liquid on the frit is usually not high enough to destroy it. M w t of the solid material will also not be able to pass through the frit. Subsequently, only the vacuum has to be released and the solvent will flow back into the flask. After washing the adapter with an additional amount of solvent, there should he little or no loss of product. Sometimes, crystallization of products inside the commercially available evaporator traps occurs, and it may he difficult to remove crystals from the inner surface of the trap. However, recovering almost any solid or liquid product from the fritted adapter is~simple. Only chemicals that attack glass, i.e., hydrofluoric acid, alkalies, and phosphoric acid, will affect the fritted adapter. Mechanical cleaning can be accomplished by reverse-flow washing. In addition, traps offered by scientific product companies occupy more space than the fritted adapter. This can be a disadvantage if additional equipment has to be combined with the rotary evaporator. The overall performance assessment of the fritted adapter is very good. Aside from the many practical advantages mentioned above, one saves about 50% of the cost of a commercially available rotary evaporator trap. ~
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Riidlger Buchkremer and Udo H. Brlnker
State University of New York University Center at Binghamton P.O. BOX6000
Binghamton, NY 13902-6000
Volume 67
Number 12
December 1990
1071
