Safety Hazards
Accidents in the laboratory are often the result of carelessness or ignorance either by you or by your neighbors. Stay alert and pay constant attention to your own and to your neighbors’ actions. The safety precautions outlined below will be worthless unless you plan, understand, and think through the consequences of every operation before you perform it. The common accidents, which often occur simultaneously, are fire, explosion, chemical and thermal burns, cuts from broken glass tubing and thermometers, absorption of toxic, but non-corrosive chemicals through the skin, and inhalation of toxic fumes. Less common, but obviously dangerous, is the ingestion of a toxic chemical. Each of these types is discussed in a general way below, and more specific reference to certain hazards will be found in the individual experiments.
1. Fire. There should never be open flames in the lab. Make it a working rule that water is the only nonflammable liquid you are likely to encounter. Treat all others in the vicinity of a flame as you would gasoline. Specifically, never heat any organic solvent in an open vessel, such as a test tube, Erlenmeyer flask, or beaker, with a flame. Such solvents should be heated in a hood with a steam bath, not a hot plate. Never keep volatile solvents, such as ether, acetone, or benzene in an open beaker or Erlenmeyer flask. The vapors can and will creep along the bench, ignite, and flash back if they reach a flame or spark.
It is your responsibility to yourself and to your neighbors to know where the nearest safety shower and fire extinguisher are located. TAs are trained in the use of fire extinguishers.
2. Explosion. Never heat a closed system or conduct a reaction in a closed system (unless specifically directed to perform the latter process and then only with frequent venting). Before starting a distillation or a chemical reaction, make sure that the system is vented. The results of an explosion are flying glass and spattered chemicals, usually both hot and corrosive.
3. Chemical and Thermal Burns. Many inorganic chemicals such as the mineral acids and alkalis are corrosive to the skin and eyes. Likewise, many organic chemicals, such as acid halides, phenols, and so forth are corrosive and often toxic. If these are spilled on the desk, in the hood, or on a shelf, call for assistance in cleaning them up.
Be careful with hot plates to avoid burns. Always assume that hot plates are HOT.
4. Cuts. The most common laboratory accident is probably the cut received while attempting to force a cork or rubber stopper onto a piece of glass tubing, a thermometer, or the side-arm of a distilling flask. Be sure to make a proper-sized hole, lubricate the cork or stopper (lubrication is essential with a rubber stopper), and use a gentle pressure with rotation on the glass part. Severed nerves and tendons are common results of injuries caused by improper manipulation of glass tubes and thermometers. Always pull rather than push on the glass when possible.
5. Absorption of Chemicals. Keep chemicals off the skin. Many organic substances are not corrosive, do not burn the skin, or seem to have any serious effects. They are, however, absorbed through the skin, sometimes with dire consequences. Others will give a serious allergic reaction upon repeated exposure, as evidenced by severe dermatitis. Be careful about touching your face or eyes in the lab; make sure your hands are clean first. Gloves will be available in the lab. However, gloves provide only a temporary layer of protection against chemicals on your skin and may be permeable to some chemical reagents, without visible deterioration. If your gloves come in contact with a chemical reagent, remove them, wash your hands, and get a new pair immediately.
6. Inhalation of Chemicals. Keep your nose away from chemicals. Many of the common solvents are extremely toxic if inhaled in any quantity or over a period of time. Do not evaporate excess solvents in the laboratory; use the hood or a suitable distillation apparatus with a condenser. Some compounds, such as acetyl chloride, will severely irritate membranes in your eyes, nose, throat, and lungs, while others, such as benzyl chloride, are severe lachrymators, i.e. they induce eye irritation and tears. When in doubt, use the hood or consult with the laboratory instructor about the use of chemicals required for your work. Specific safety information about chemicals used is included in each experiment write up. MSDS (Material Safety Data Sheets) are available on the DCIS file server and summarize safety information about substances used in the lab.
7. Ingestion of Chemicals. The common ways of accidentally ingesting harmful chemicals are: (1) by pipet, (2) from dirty hands, (3) contaminated food or drink and (4) food use of chemicals taken from the laboratory. Below are ways to avoid accidental ingestion of chemical reagents.
• Pipets must be fitted with suction bulbs to transfer chemicals. DO NOT USE MOUTH SUCTION.
• Wash your hands before handling anything (cigarettes, chewing gum, food) which goes into your mouth. Wash your hands when you leave the laboratory.
• Do not eat or drink in the laboratory. Use the water fountains for a drink–not a laboratory faucet. Remove gloves and wash your hands before using the water fountain or bathroom.
• Never use chemicals (salt, sugar, alcohol, bicarbonate, etc.) from the laboratory or stockroom on food. The source containers may be contaminated or mislabeled.
• Never use laboratory glassware as a food or drink container.
• Never store food or drink in a laboratory refrigerator or ice machine. Never consume ice from a laboratory ice machine.
Font: Darmouth College web
http://www.dartmouth.edu/~chemlab/info/safety/hazards.html
