A Homemade Stirring Bar tor Magnetic Stirrers In schools and colleges where a number of magnetic stirrers are used, the number of stirring bars lost every year can be a big headache to teachers. Inexpensive stirring bars can be made by sealing iron wire into pieces of glass tubing. However, successfully sealing both ends of the glass tubing is not easy because, after one end is sealed, the hot air expanded from the other end often blows an opening on the seal or f o r m a thin bubble on this second end. Thus either the stirring bar being made has a bole on one end or is very fragile. We have found a method to avoid the hot air from blowing out of the second end of a glass tubing when it is sealed. A piece of glass tubing about 20 cm inlength is used. After one end is sealed, apiece of thickiron wire (e.g., 1cm of B&S 18-gaugewire) is slipped into the glass tubing. Then the other end of the glass tubing is attached to a piece of rubber tubing connected to a water aspirator. When the water is turned on, the air in the glass tubing is evaculated. With the water aspirator continuously evaculating air, the glass tubing is sealed near the second end of the iron wire. When the glass is melted, the molten glass contracts to the iron wire and gathers there. No bubble is produced because the air pressure inside the glass tubing is less than the atmospheric pressure outside. Xlaorong LI Shaanxl Teachers University Xian, Shaanxi, PRC James C. Chang University of Northern Iowa Cedar Falls, Iowa 50614
346
Journal of Chemical Education
