overhead projector
edited by
DORISKOLB Bradley University Peoria, lL61625
Iodine Demonstration of Sublimation Robert H. Goldsmith St. Mary's College of Maryland St. Mary's City, MD 20686 The process of sublimation, in which a solid is directly converted into the gaseous state, is a n interesting and impressive phenomenon. It can be demonstrated readily using a n overhead projector. The element iodine provides a simple way to demonstrate sublimation in the classroom. Procedure A small amount of solid iodine is placed in a 10-mL beaker. This beaker is then placed inside a 250- to 400-mL
1132
Journal of Chemical Education
beaker that has been filled with ethanol or isopropanol up to a level of 1.5 to 2 cm from the bottom of the beaker. A watchglass or glass plate can be placed on the top of the beaker as a cover. This setup can now be placed on the stage of a n overhead projector and the image can be projected onto a nearby screen. Within a few minutes a light pink color may be observed on the screen. This demonstration may now be allowed to proceed a s the class continues. Within 15 to 20 min the alcohol begins to take on a definite yellowish tint. The color intensities as time progresses and becomes a yellowish-tan color. This demonstration clearly shows the dissolution of the iodine vapor, which could come only from the solid iodine. I t is a quick, easy to perform, and effective demonstration of the process of sublimation.
