The Boiling Tube While standard-tapered glassware has largely replaced cork and rubber stopper fittings in the organic laboratory, the devices employed for smooth ebullition of solvents or solutions a t atmospheric pressure seem antiquated by eomparison. A random survey of sixteen lab manuals revealed that bailing chips, Teflon balls, wooden splints, and glass wool are commonly recommended. Each has its drawback, especially during a crystallization procedure in which a solution must be concentrated by boiling. Removal of any of the given materials before crystallization begins means certain loss of some of the solution. For years our students have employed a boiling tube which this writer first saw in use during his graduate work a t Brown University. The tube is made by fusing a 10- to 15-mm length of 6-mm Pyrex tubing onto a 6-mm Pyrex glass rod of any length. Insertion of the tube into a liquid to be boiled provides a steady flow of air bubbles, hence smooth boiling. The tube is as durable as any glass item when properly handled; it does not contaminate the solution, and it can be mass-produced cheaply by anyone with a n elemental knowledge of working glass. The most important advantage is its ease of removal from a solution from which crystallization is t o occur. A rinse with a small amount of the solvent ensures no material loss. An additional plus lies in the fact that the solid end of the tube may be used as a stirring rod. Tucker has described' a somewhat fragile "distillation bubble" which performs the desired function hut whose preparation is unnecessarily complicated and time-consuming. Knoebe12 suggested a U-shaped tube of 5-mm glass but this will not fit into small Erlenmeyer flasks. Also, if one forgets to remove this device before the solution cools mueh of the liquid will be drawn up into the tube. We could not find a commercially available boiling tube in any of thirteen catalogs that were cheeked." The tube described here is a scaled-up version of one suggested for use in miero-boiling point determinations.' Since the student of organic chemistry spends mueh of his or her time performing distillations and concentrating solutions, we suggest that it can be done more efficiently and with style by use of the boiling tube instead of those devices described in lab manuals. Tucker, S. H., J. CHEM. EDUC., 26,546 (1949). Knoebel, A. B., Chem. Analyst, 19,20 (1930) as abstracted in J. CHEM. EDUC., 7,683 (1930). However, one (Sargent-Welch, Catalog 119, p. 672) offers a boiling point capillary with two feet, appendages that are not needed on a micro tube. Shriner, R. L., Fuson, R. C., and Curtin, D. Y., "The Systematic Identification of Organic Compounds," 5th ed., John Wiley & Sons, Inc., New York, 1964, p. 37. Gettysburg College Gettysburg. Pennsylvania 17325
50 / Journal of Chemical Education
A. T. Rowland
