Ground Glass Joints-Tape
and Clip Them But Don't Grease Them!
A recent note describes a method for unfreezing ground joints which have become stuck ( I ) , and another describes a method to remove grease from glass joints (2).I would like to point out that there has long been a way to avoid frozen joints without using grease. The Aldrich Chemical Company offers Teflon tape for the express purpose of eliminating the need for grease on ground glass joints. We overlap a single wrapping of the 0.5-in. wide tape (Order No. 210,438-8) on the top half of the inner 19/22joint with excellent results. These joints do not get stuck when using Teflon tape under any conditions, including vacuum distillation and reflux of caustic solutions. While on the subject of glass joints, I would also like to relate our experience with the use of Keck joint clips (Aldrich Order No. 215,0434 for 19/22joints). We include three clips, costing $2.27 each, as part of the desk equipment in organic laboratory. These enable the student to assemble the typical distillation apparatus, in less time, by clipping the condenser to the three-way still head, thereceivingadapter to the wndenser and the receiving flask to the receiving adapter before the entire assembly is attached to the Claisen head or fractionating column. Voila-an end to rubber bands, dangling flasks and lost distillate due to separated joints. Fewer ringstands and jaw-type clamps have to be used, and, best of all, reduced breakage pays far the clips many times over. Students seldom need to be reminded to use the clips because they are easy to use and very effective. In fact, you have a hard time convincing them that they really don't need to clip that reflux wndenser to the reaction flask! Literature Cited 1. Bmam, T.;Sund, E. H.J Chorn. Edue. 1992,69,421 2. Nmaya"an,N. J. Chern.Edu 1992,m, 9.849.
Josef G. Krause Niagara University, NY 14109
Volume 70 Number 7 July 1993
589
