Due to their corrosive nature, they can irritate or even burn the eyes, irritate the skin, and cause respiratory distress. The risk is higher when they are concentrated, but even when diluted they can be hazardous. Protective equipment, including chemical goggles, aprons, and gloves, is essential. The teacher should research the handling of specific acids or bases by studying the SDSs before using them.
- Acids—hydrochloric acid, nitric acid, sulfuric acid, acetic acid, phosphoric acid
- Bases—sodium hydroxide, potassium hydroxide, ammonia
These are chemicals or organisms that increase the rate at which natural biodegradation occurs. They have the ability to adversely affect human health in a variety of ways, ranging from relatively mild, allergic reactions to serious medical conditions, even death. They should be handled only by teachers with the knowledge and skills to work with them safely. They are not recommended for use in the pre-college setting.
Examples: bacteria, fungi
These are not common in the pre-college setting. The compressed gas cylinders come in all sizes. High school laboratories generally use lecture bottles rather than large gas cylinders, which require the use of special pressure regulators and valves. The cylinder should always be kept secured. The cap should always be on when not in use. The valves and regulators should be routinely checked for leaks.
Examples: Helium, nitrogen, carbon dioxide, hydrogen, oxygen
Electricity has long been recognized as hazardous. It can cause electric shock, electrocution, burns, fires, and even explosions. Ideally, all of the electrical circuits in a science laboratory should include ground fault circuit interrupters (GFCIs), which are designed to protect people from electrical hazards. Any electrical circuits used for measuring conductivity, or similar circuits, unless they are battery-powered, must contain a momentary switch. The teacher should ensure that all electrical devices are functioning properly and that the electrical cords are in good condition.
Examples: hot plates, magnetic stirrers, any equipment plugged into an electrical outlet
These are most commonly used in the laboratory as solvents. Never use any type of open flame or any source of ignition around flammable chemicals.
Note: It is the vapors from flammable liquids that are flammable, and when one opens a bottle of flammable liquid, the first thing that leaves the bottle is the vapor (flammable part) from the top of the bottle.
Examples: acetone, ethanol, ethyl acetate, hexane, methanol
These elements are highly reactive, toxic, corrosive, and capable of irritating the skin. In the pre-college setting, they should only be used in small quantities by the teacher in a well-ventilated hood, using appropriate PPE and with an appropriate reducing agent (sodium thiosulfate) present to clean up spills.
Examples: fluorine, chlorine, bromine, iodine
Note: Fluorine is extremely poisonous and requires special equipment and handling.
These compounds are combustible or flammable and can irritate the skin. Used in a confined space, they can cause asphyxiation. They should always be used in a well-ventilated area (or with a hood) and away from any open flames. Flammables and combustibles must never be heated on a hot plate.
Examples: hexane, pentane, petroleum ether, acetone, methanol, ethanol
Mercury is a serious chronic health hazard. Although it is not readily absorbed through the skin, its greatest health hazard is due to inhalation of its vapors, usually as a result of a spill. All mercury or mercury-containing devices should be removed from the pre-college laboratory. Mercury compounds (e.g., alkyl mercury) are extremely toxic and must be handled with extreme care.
Examples: mercury-in-glass thermometers and barometers
An oxidizing agent is a substance that causes oxidation, or the loss of electrons from an atom, compound, or molecule. A reducing agent is a substance that causes reduction, or the gain of electrons. Oxidation and reduction always occur together. Oxidation-reduction reactions tend to release heat, so oxidizers and reducing agents can cause other materials to combust more readily. Always store oxidizing and reducing agents away from each other and from flammable materials. Look up which substances are incompatible in the SDSs.
Note: Mixing oxidizing agents (nitric acid) with organic materials in waste bottles has resulted in many explosions.
- Oxidizing agents—chlorates, chromates, dichromates, hypochlorites, nitrates, nitric acid, nitrites, perchlorates, permanganates, peroxides
- Reducing agents—alkali metals, alkaline earth metals, hydrogen gas, carbon monoxide
These are a group of chemicals that have an oxygen-to-oxygen bond (R–O–O–R). Care must be taken when handling inorganic or organic peroxides, since they tend to be unstable and can, depending on the compound, decompose violently. Some peroxides are used as reactants, but peroxides as contaminants in other chemicals are also a concern. Peroxides that contaminate organic solvents are of particular concern. Peroxides form slowly in some organic solvents, and as their concentrations increase they present a greater hazard. At the pre-college level, it is best to avoid using or storing these organic solvents. Should these compounds be needed, only the quantity needed for experiments should be ordered so that there is no need for storage.
- Common peroxides used in the pre-college setting—hydrogen peroxide, H2O2
- Peroxide-forming substances to avoid—ethers, alkenes, secondary alcohols, ketones, alkali metals
These are substances that readily ignite and burn in air spontaneously. These substances have no place in the pre-college setting. They should be handled only by chemists with the knowledge and skills to work with them safely.
Examples: white phosphorus, alkali metals and their compounds