Nanotechnology 5.27 A chemistry student accidentally drops a large mercury therm

Question

Nanotechnology

5.27 A chemistry student accidentally drops a large mercury thermometer and it breaks. The thermometer contained 2 g mercury (Hg), a potent neurotoxin. The Hg leaks out and pools together into a droplet on the floor of the laboratory. The Occupational Safety and Health Administration (OSHA) sets the permissible or mercury vapor in air at 12 ppb, by volume. At no tme should anyone be exposed to mercury vapor above this threshold. The molar mass of Hg is 201 g/mol. The temperature and pressure in the lab are 14.7 psia and 70°F, respectively

Explanation / Answer

It is HMC policy that when a spill occurs, the responsibility for having the spill cleaned up rests with the person causing the spill. If the individual responsible is or unable to clean up the spill for any reason, then responsibility for assessing the spill rests with the Department. Contact the Chemical Hygiene Officer for assistance.

If the spill is large, complicated, toxic, or fumy, and occurs outside of the fume hood, a hazardous materials team may be called in for assistance. Custodians are not permitted to clean up spills of hazardous materials.

Experiments should always be designed so as to minimize the possibility of an accidental release of hazardous substances. Plan your experiments to use the minimal amounts of hazardous compounds practical and alwaystransport such materials properly using break-resistant bottles or secondary containers.

As discussed further below, develop a contingency plan to handle spills when working with hazardous substances. In the event a spill does occur, the following General Guidelinesfor Handling Spills should be followed in the indicated order of priority. Tend to any injured or contaminated personnel and if necessary request help (Campus Safety x.72000).

Notify other personnel of the accident and if necessary evacuate the area. Use the buddy system when attending to a spill. Take steps to confine and limit the spill if this can be done without risk of injury or contamination. Prevent spill from entering sinks or drains. Clean up the spill using adsorbent and/or neutralizing materials.

Dispose of contaminated material properly as hazardous waste. Clean spill area with detergent and water. The following section outlines specific procedures for handling the accidental release of hazardous substances.

Mercury

The element mercury is a liquid metal with a vapor pressure of 0.00185 mm at 25oC. This corresponds to a saturation concentration of 20 mg of mercury per cubic meter of air or 2.4 ppm of air. The ACGIH has established a TLV for mercury vapor of 0.05 mg/m3 for continuous 40- hour per week exposure.

Long-term chronic exposure to mercury vapor in excess of 0.05 mg/m3 may result in cumulative poisoning. The use of mercury in laboratory amounts in well-ventilated areas is fairly safe; however special precautions must be followed when working with large quantities of mercury. Mercury poisoning from exposure by chronic inhalation produces a variety of symptoms. The characteristic effects are emotional disturbances, unsteadiness, inflammation of the mouth and gums, general fatigue, memory loss, and headaches. Kidney damage may result from poisoning by mercury salts.

In most cases of exposure by chronic inhalation, the symptoms of poisoning gradually disappear when the source of exposure is removed. However, improvement may be slow and complete recovery may take years. Skin contact with mercury produces irritation and various degrees of corrosion. Soluble mercury salts can be absorbed through the intact skin and produce poisoning.

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