composition consists of heating a small sample in a melting-point tube.
• A reactant is capable of self-polymerization.
• A reaction is delayed; that is, an induction period is required.
• Gaseous byproducts are formed.
• A reaction is exothermic. What can be done to provide, or regain, control of the reaction if it begins to run away?
• A reaction requires a long reflux period. What will happen if solvent is lost owing to poor condenser cooling?
• A reaction requires temperatures less than 0 °C. What will happen if the reaction warms to room temperature?
• A reaction involves stirring a mixture of solid and liquid reagents. Will magnetic stirring be sufficient at large scale or will overhead mechanical stirring be required? What will happen if stirring efficiency is not maintained at large scale?
In addition, thermal phenomena that produce significant effects on a larger scale may not have been detected in smaller-scale reactions and therefore could be less obvious than toxic or environmental hazards. Thermal analytical techniques should be used to determine whether any process modifications are necessary.
Consider scaling up the process in multiple small steps, evaluating the above issues at each step. Be sure to review the literature and other sources to fully understand the reactive properties of the reactants and solvents, which may not have been evident at a smaller scale.
6.C.8 Responsibility for Unattended Experiments and Working Alone
It is prudent practice to avoid working alone at the bench in a laboratory building. Individuals working in separate laboratories outside normal working hours should make arrangements to check on each other periodically, or ask security guards to check on them. Experiments known to be hazardous should not be undertaken by a person who is alone in a laboratory. Under unusually hazardous conditions, special rules, precautions, and alert systems may be necessary. (See also Chapter 2, section 2.C.2.)
Laboratory operations involving hazardous substances are sometimes carried out continuously or overnight with no one present. Although unattended operations should be avoided when possible, personnel are responsible for designing experiments to prevent the release of hazardous substances if utility services such as electricity, cooling water, and flow of inert gas are interrupted.
For unattended operations, laboratory lights should be left on, and signs should be posted identifying the nature of the experiment and the hazardous substances in use. If appropriate, arrangements should be made for other workers to periodically inspect the operation. Information should be posted indicating how to contact the responsible individual in the event of an emergency.
6.C.9 Chemistry Demonstrations and Magic Shows
All planned demonstrations and chemistry magic shows that will be performed by chemistry personnel that are not a part of normal laboratory activities should be preapproved and authorized by the organization and should follow all institutional policies. Activity organizers should obtain safety advice from experts as necessary. Experienced chemists who are interested in participating in such activities and want to use the organization’s chemicals and apparatus should submit an activity plan in advance of the event. This plan should include
• location of the demonstration,
• date of the event,
• age of the intended audience,
• number of persons who will attend the event,
• degree of audience participation,
• demonstrations that will be performed,
• list of chemicals that will be transported to the demonstration site, and
• PPE that will be worn and by whom.
All chemicals must be transported in accordance with U.S. Department of Transportation regulations, if applicable, and must be handled in a prudent manner, packaged appropriately, labeled properly, and transported back to the institution for disposal via the institution’s chemical waste disposal system. Under no circumstances should any chemicals be left at the demonstration site or disposed of there. Prior to the planned event, organizers should ensure that, if an accident involving chemicals occurs in their personal vehicles, they will be covered under their private insurance policies.
[For more information about safety when performing chemistry demonstrations, see the American Chemical Society’s NCW and Community Activity SAFETY GUIDELINES (available at http://portal.acs.org/).]