Solvent-Saving Procedure for Removing Tar from DistlllatlonFlasks Removing tar from a distillation flask can he a frustrating and solvent-consuming experience. The following procedure is generally an improvement. Insert, for example, a 1-L, 1-neck, round-bottomed flask containing residue into a 100-mL beaker filled to about 80 mL with acetone or other volatile solvent as shown. The liquid level may later be raised, if needed, by squirting in additional acetone from a wash bottle. Ideally, the shoulders of the flask rest on the top of the beaker and there is a small gap hetween the end of the flask joint and the bottom of the beaker. For long-necked flasks, use a tallform beaker or clamp the flask to a ring stand. Alternately, if the flask neck is too long for the beaker, insert a bent piece of wire under the joint to permit solvent flow. Depending upon atmospheric pressure change and temperature variation, the acetone level will ascend and descend the neck of the flask. If there is some solubility of the tar, the vapor inside the flask will gradually loosen it so that it flows into the solvent and within a few hours most of the tar is removed. The process may be accelerated by pre-warming the flask or heating the flask with a heat gun after it is in place. This
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will cause acetone to be drawn higher into the flask on cooling.
E. J. Elsenbraun Oklahoma State Universihl Stillwater. OK 74078
Volume 63
Number 6 June 1986
553
