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CHEMICAL SAFETY IN THE CLASSROOM LAB—by Anne WallingfordFollowing safety rules is of paramount importance in the chemistry lab. It cannot be stressed too often that you, as the lab instructor, are ultimately responsible for your students' safety. In almost every state, teachers—as well as the school—are legally liable for student injuries. The following guidelines will help you maintain a safe chemistry lab. 1. Read the label. Read the label twice. The first safety step in any chemistry lab is to develop the habit of reading labels. Look for the warnings. All major school suppliers of chemical supplies in the United States use color-coded HMIS (Hazardous Materials Identification System) labels. The HMIS indicator shows the hazards of the chemical in-use, not just fire-related hazards. You can learn more about HMIS labels and how to read them at The MSDS Hyper Glossary page from Safety Emporium.
2. Know the potential hazards of a chemical before using the substance in the classroom. Before using unfamiliar chemicals, study the MSDS for the chemical being used. What is an MSDS? The Material Safety Data Sheet, or MSDS, is a detailed document prepared by the manufacturer or packager of a hazardous substance. The MSDS describes both the physical and chemical properties of a product, and is used with any hazardous material, even those not used in a chemistry lab. Legally, the school is required to maintain an MSDS file for every chemical used in the building. This includes the chemistry lab, the art room, and the janitor's closet. An MSDS should be obtained for every chemical used in the lab, and the MSDS file should be easily accessible in case of an emergency. An MSDS can be requested from the seller of the chemical if it is not supplied when you purchase the chemical. (New laws allow the customer to receive the MSDS electronically by requesting it from the seller's website.) Clarion University of Pennsylvania has an excellent explanation of the MSDS. Go to: http://www.clarion.edu/admin/publicsafety/MSDSFrontPage.shtml (link will open in a new window). East Carolina University of Greenville NC web page, Guide to Your Material Safety Data Sheet has a detailed explanation of how to read an MSDS (link will open in a new window). 3. Label everything. This is especially important if you routinely store chemicals in smaller containers for easy classroom distribution. You can make your own labels or you can purchase preprinted Right to Know labels for your storage containers. The label should include the chemical name (no abbreviations), the concentration (if needed), the date prepared and the name of the preparer. No hieroglyphics allowed. Another alternative that is both safety and cost effective is to purchase chemicals in smaller amounts. Determine the real need for the chemical for the next year, and only purchase what you need for a year or for the shelf life, to avoid waste and potential disposal charges. (Some chemicals have very a short shelf life. For example, hydrogen peroxide 30% has a 6 month or less shelf life.) Purchasing in small quantities will drastically reduce, or even eliminate, storage and disposal problems. Again, most major chemical suppliers offer chemicals in small sizes. 4. Buy only the safety bottles when purchasing strong corrosives. 5. Do not return any leftovers to the original container. When transferring chemicals from a large container to a smaller container, it is tempting to pour leftovers back into the original container. Don't do it. 6. Learn how to safely dispose of chemicals. Only nonflammable, non-toxic, water-soluble chemicals can be flushed down the sink or toilet. The primary guideline for disposal is local ordinance, then the state EPA. OSHA has the Lab Standard, but that does not really cover disposal in depth. When in doubt, start local, since local codes can over-ride the state ones. And yes, safe disposal of chemicals will cost money. Your local school board and the school principal need to be made aware of this requirement and budget accordingly. 7. Store chemicals safely. First separate all oxidizers, acids, poisons, flammables and general storage chemicals so as to minimize interactions. Use a color code system like that commonly used in industry and education:
8. Store flammables, volatile liquids, and reactive chemicals in color-coded, labeled storage cabinets. Both the storage cabinets and the room the storage cabinets are in should be kept locked at all times. 9. Always keep a current inventory of the chemicals stored in the Prep Room or in the chemical storage room. Actually, an inventory of all chemicals in each room is best. The inventory should be kept in the room, and in the front office. Some fire departments require the inventory to be filed with them so they know what is in the room before entering the building. 10. Use a fume hood whenever hazardous vapors will be released. (See the article The Importance of Classroom Lab Safety for more information on fume hoods.) Also, Labconco has a free book on fume hoods that can be downloaded (Labconco link will open in a new window). 11. Always add concentrated solution to less concentrated solutions. Use the alphabet rule as a memory aid: Acid (A) is added to water (W). 12. Promptly clean up any chemical spills using appropriate absorbents. For chemical spills, there are a variety of spill control kits available from science education catalogers. Spill control pads are useful for small chemical spills. Mercury spill sponges soak up mercury and the mercury can be drained into a collecting jar. (Even a broken mercury thermometer presents a safety hazard.) You can also make a spill control kit by purchasing sodium bicarbonate for acids (2.5 kg) and vinegar for base spills. Citric acid (base spills) and sodium carbonate (acid spills) are also useful. For an absorbent, use vermiculite (usually packed around the chemical bottles for shipping.) 13. Substitute non-hazardous chemicals for hazardous ones whenever possible. An excellent reference guide can be found at the Hazardous Waste Management for King County (Seattle) site, Rehab the Lab (link will open in a new window). Remember, safe labs don't pollute! 14. Use safe techniques for transferring chemicals from one container to another.  A. Wear the appropriate gloves. (See the article The Importance of Classroom Lab Safety for more information on gloves.) B. Read the bottle label. Read the MSDS. Read the label again. C. Place a glass stirring rod into the receiving container. The rod should lean against the inner wall of the container. D. Remove the stopper from the container. To reduce the risk of contamination, do not place the stopper on the lab bench. Instead, hold the stopper between the third and fourth fingers of your pouring hand. E. Turn the bottle's label towards your pouring hand. Pick up the bottle. F. Tilt the bottle until its lip touches the stirring rod. (See Drawing.) Gently pour the liquid reagent down the stirring rod into your container. F. Restopper the bottle. G. Label the new container.  A. Wear the appropriate gloves. (See the article The Importance of Classroom Lab Safety for more information on gloves.) B. Read the bottle label. Read the label again. C. Remove the lid from the bottle. Place the lid upside down on the lab bench. D. Turn the bottle's label towards your pouring hand. Pick up the bottle. E. For a granular substance, you can tilt the bottle and roll it gently to pour contents into the new container. Do not insert a spatula into the original container. Do not return extra material to the original container.
An even better method—one that works with both granular substances and those clumped due to moisture, etc.—would be to use a very clean spatula or scoopula, remove the chemical from the bottle holding the bottle's neck over the beaker and then dump the material from the spatula into the beaker. Again, do not return material to the bottle, even from the spatula. F. Recap the original bottle. G. Label the new container. 1. The most commonly used hazardous chemicals: ** Indicates a suspected carcinogen Asbestos * (No longer legal to possess.) Benzene * (No longer legal to possess.) Carbon Disulfide Carbon Tetrachloride ** (No longer legal to possess.) Chromium and Chromium Compounds * Chlorine Chloroform ** Ethylene Thiourea ** Formaldehyde ** Hydrogen Sulfide Lead Acetate ** Lead Chloride Lead Phosphate ** Mercury and mercury compounds Nickel ** Potassium Chromate Saccharin Silver Nitrate Thiourea 2. Commonly used oxidizers that need to be stored away from other chemicals: Barium Peroxide Hydrogen Peroxide, 30% Potassium Chlorate Potassium Permanganate 3. Chemical Grades, from highest grade to lowest
4. Standard Abbreviations
When purchasing chemicals, use the grade and type required in the experiment's directions. Different grade levels or types can produce unexpected, and sometimes unwelcome, results. 5. Common Chemical Nicknames
6. Chemicals requiring special handling
7. General comments
Quick conversions
Other Useful Resources The ACS's Chemical Safety for Teachers and their Supervisors Safety Handbook is free by writing to the ACS (American Chemical Society) and asking for it, or you can purchase multiple copies. There are two versions of the handbook, one for students and one for the teacher. You can find the book at the ACS web site (link will open in a new window); use the committee on chemical safety tab. Special thanks go to Ken Thompson., Chief Chemist, ScholAR Chemistry, Retired, who acted as technical consultant for this article.
© 2004 Anne Wallingford. All rights reserved.
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Saturday, August 09, 2008
