Potentially Teratogenic Metals

Lead is a solid that melts at 327°C. Simply handling pieces of lead shot or lead foil should pose no appreciable health risk for students. Mercury. on the other hand, is a liquid of significant vapor pressure, and working with metallic mercury is known to be hazardous. The long term risk of breathing mercury vapor applies to all students, but there is a special, more immediate risk for the student who happens to be pregnant. 

Typical exposure to mercury in the General Chemistry laboratory occurs during (A) Boyle s Law experiments, (B) thermal decomposition of mercuric oxide, (C) displacement of mercury from its dissolved salts, and (D) cleaning up spills from broken thermometers. 

Thermal decomposition of mercuric oxide (B) 1s a classic experiment that is very much worthwhile in the freshman laboratory. It is an excellent example of how different a compound can be from its component elements. It is also the historical reaction that Joseph Priestley carried out when he discovered oxygen. However, it need not be done individually by every student. If the instructor demonstrates this experiment, the students exposure to mercury is greatly reduced. (Note that this experiment generates hot mercury vapor, which is more hazardous than the same amount of cool liquid mercury.) This reaction could also be shown to students by means of a film strip or video tape. 

The displacement of mercury from a dissolved mercury salt (C) using a metal such as copper, for example, might easily be substituted by the similar displacement of silver from silver nitrate solution. 

Occasional accidents involving broken thermometers (D) are almost inevi- 

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