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Prudent Practices in the Laboratory: Handling and Disposal of Chemicals
nents. Sometimes halogenated and nonhalogenated wastes must be segregated for separate handling.
The container used for the collection of liquid waste must be appropriate for its use. Glass bottles are impervious to most chemicals but present a breakage hazard, and narrow necks can cause difficulty in emptying the bottles. The use of plastic (e.g., polyethylene jerrycans) or metal (galvanized or stainless steel) safety containers for the collection of liquid waste is strongly encouraged and, indeed, required for flammable liquids.
Galvanized steel safety cans should not be used for halogenated waste solvents because they tend to corrode and leak. Flame arresters in safety cans can easily become plugged if there is sediment and may need to be cleaned occasionally.
Waste containers should be clearly and securely labeled as to their contents and securely capped when not in immediate use.
Aqueous waste should be collected separately from organic solvent waste. Some laboratories may be served by a wastewater treatment facility that allows the disposal of aqueous waste to the sanitary sewer if it falls within a narrow range of acceptable waste types. Thus, solutions of nonhazardous salts or water-miscible organic materials may be acceptable in some localities. Solutions containing flammable or hazardous waste, even if water-miscible, are almost never allowed, and water-immiscible substances must never be put down the drain. Aqueous waste for nonsewer disposal should be collected in a container selected for resistance to corrosion. Glass should not be used for aqueous waste if there is danger of freezing. Depending on the requirements of the disposal facility, adjustment of the pH of aqueous waste may be required. Such adjustment requires consideration of the possible consequences of the neutralization reaction that might take place: gas evolution, heat generation, or precipitation.
Solid chemical waste, such as reaction by-products, or contaminated filter or chromatography media, should be placed in an appropriately labeled container to await disposal or pickup. Unwanted reagents should be segregated for disposal in their original containers, if possible. If original containers are used, labels should be intact and fully legible. Every effort should be made to use, share, or recycle unwanted reagents rather than commit them to disposal. (See Chapter 4, sections 4.D and 4.E, for a discussion of labeling alternatives.)
Nonhazardous solid waste can be disposed of in laboratory trash or segregated for recycling. Institutional policy should be consulted for these classifications. (See Chapter 7 for further information regarding disposal, and check the appropriate LCSS to determine toxicity.)
5.C.7Use and Maintenance of Equipment and Glassware
Good equipment maintenance is essential for safe and efficient operations. Laboratory equipment should be inspected and maintained regularly and serviced on schedules that are based on both the likelihood of and the hazards from failure. Maintenance plans should ensure that any lockout procedures cannot be violated.
Careful handling and storage procedures should be used to avoid damaging glassware. Chipped or cracked items should be discarded or repaired. Vacuum-jacketed glassware should be handled with extreme care to prevent implosions. Evacuated equipment such as Dewar flasks or vacuum desiccators should be taped or shielded. Only glassware designed for vacuum work should be used for that purpose.
Hand protection should be used when picking up broken glass. Small pieces should be swept up with a brush into a dustpan. Glassblowing operations should not be attempted unless proper annealing facilities are available. Adequate hand protection should be used when inserting glass tubing into rubber stoppers or corks or when placing rubber tubing on glass hose connections. Cuts from forcing glass tubing into stoppers or plastic tubing are the most common kind of laboratory accident and are often serious. Tubing should be fire polished or rounded and lubricated, and hands should be protected with toweling and held close together to limit movement of glass should it fracture. The use of plastic or metal connectors should be considered.
Flammable substances present one of the most widespread hazards encountered in the laboratory. Because flammable materials are employed in so many common laboratory operations, basic prudent laboratory practice should always assume the presence of fire hazard unless a review of the materials and operations in the laboratory verifies the absence of significant hazard. For example, simple operations with aqueous solutions in a laboratory where no flammable organic liquids are present involve no appreciable fire hazard. In all other circumstances, the risk of fire should be recognized and kept to a minimum.
For a fire to start, an ignition source, fuel, and oxidizer must be present. Prudent laboratory practice in avoiding fire is based on avoiding the presence of one of these components. The flammability and explosive characteristics of the materials being used should be