safety-in-academic-chemistry-laboratories-students

You can evenly heat best by using a ceramic cavity

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Unformatted text preview: accident-prevention factor in the distillation process. You can evenly heat best by using a ceramic cavity heater, steam coils, hot water, a nonflammable liquid bath, or an electric heating mantle. Before using a heating mantle, inspect it for rips, tears, loosened seams, and severe distortions of the covering cloth. Do not use a mantle with any of these defects. Silicone oil or another suitable high-boiling oil also can be used for even heating on a hot plate. Commonly available hot plates are not necessarily spark-proof; make sure they are so labeled. When distilling a flammable liquid, do not use a hot plate unless you are certain it is spark-proof. Sometimes a distillation will go awry. When this happens, it is often desirable to remove the heat source from underneath the distillation apparatus. Therefore, support the distillation apparatus separately from the heat source to facilitate its removal if necessary. An additional thermometer may be inserted very near the center bottom of the distilling flask to warn of dangerous exothermic reactions. To prevent such reactions, do not heat the material above the temperature directed in the procedure you are following. Never distill organic compounds or evaporate them to dryness unless they are known to be free of peroxides. Most ethers, including cyclic ethers, form dangerously explosive peroxides on exposure to air and light. Many alcohols, unsaturated hydrocarbons, and other reagents also can form peroxides. See “Organic Peroxides and Peroxide Formers” on page 24. See “Working with Reduced Pressure” on page 31 for a brief discussion on distilling under reduced pressure. See “Using Steam” on page 28 for a brief discussion on steam distillation. Extractions Extractions can present a hazard because of the potential buildup of pressure from a 7 students short index 1/15/03 12:45 PM Page 8 volatile solvent and an immiscible aqueous phase. Glass separatory funnels used in laboratory operations are particularly susceptible to problems because the...
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This document was uploaded on 02/27/2014 for the course PHYS 1B at UCSD.

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