An Automatic Water Trap for Steam Distillation The most common source of steam for student steam distillations is steam lines. Unfortunately, this steam is accompanied, intermittently, by water, which (even were it not contaminated with rust and unidentified, oily material) is best kept out of the distillation apparatus. The separation of steam from water is accomplished by a water trap, frequently consisting of a two-hole stopper (with heavy-walled tubing for conducting steam to and from it) inserted in a gwseneck to which is attached a thin-walled tube for draining water. Commonly, this draining tube is closed witha screw elampuntil the trap is almost full of water. If all the water is allowed todraiu, steam can escape. This is disadvantageous because, instead of entering the distillation apparatus, the escaping steam can heat the tuhe and clamp and scald the student. If the student is distracted, inattentive, or otherwise occupied when the trap fills, the contaminated water is swept into the distillation apparatus. I t is probably the rule rather than the exception that at least one of these mishaps will occur st least once during the course of a student's steam distillation. Consequently, steam distillations provoke anxiety and frustration in students. The unpleasant aspects of the water trap can he avoided with a simple, inexpensive device that renders the water trap automatically selfdraining. This device consists of an inverted Y-tube placed so that the vertex of the Y is below the maximum height to which the water in the trap may he permitted to rise. One downward-pointing arm of the Y-tube is connected to the lower end of the gooseneck by a water-filled tube of sufficient lengthso that the resultingloop will provide enough of a head to halance the pressure of the steam and prevent the steam from escaping. The other downward-pointing arm is fitted with a tuhe running to the drain without impediment. The third, upward-pointing, arm of the Y-tube admits sir to prevent siphoning and has an open ruhher tuhe running upward from it to mitigate the effect of pressure surges. All tubes used for this device are condenser tubing. Ben Ruekberg The University of Rhode Island Kingston. RI 02881
88
Journal of Chemical Education
