edited by MIRIAM C. NAGEL Avon High School Avon. CT 06001
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Consider Safety as an Active Process L. C. Mehlhaff and Keith 0. Berry University of Puget Sound Tacomg WA 98416
Most statements of advice to teachers and students are presented in the form of a list of rules. One may use a check list of some sort to survey the lahoratory and classroom soace to accomolish a oeriodic "Safetv Audit".' While such devices are u s e h toois for specific circumstances, any list suffers because it does not involve each participant (student and teacher1 i n t h r o r l i ~ e p r o w a sthat isessential for Iahoratorv wurk. The nature dlahorators work i i tu particivate in sol;ing a problem, and lahoratory safety mustbe seen as an activity in which one must participate at all times. The part of laboratory activity called "Safety" actually has several aspects, such as knowing the potential sources of risk, developing a plan to reduce those potential risks, and working in the laboratory to fulfill that plan. The conscious development of a suitable safety program rests on two precepts: (1) If anything can go wrong, it will (Murphy's Law); and (2) There are few real "accidents" in the lahoratory. Most "accidents" are the result of poor planning or carelessness. Teachers have a responsibility to seek out potential problems, to analyze lahoratory procedures, and to inform students of potential pitfalls. They also have a responsibility to inform those accountable for the maintenance of a safe laboratory space of problems that should he c o r r e ~ t e dWheth.~ er secondary school or university, the principles of safe lahoratory management are much the same. We suggest four domains of emphasis that will help the teacher establish safe practices in the laboratory: The Physlcal Facilltles This is the laboratory environment. In our laboratories we try to identify "operational zones", which are physical areas separated by function. That function must he simple and discrete. We separate reagent acids and bases into distinct storage areas. Instruments are separated from the zones where reagents might cause corrosion. Work stations are separated sufficiently one from another so that students will not interfere with each other. The increased quality of education is an argument for, limiting the number of students in a class. A stronger argument for reasonable class size can often he made on the basis of safe laboratory practice. I t has been said that the standards for liahilitv are measured against the standard of whether a reasonably prudent person, operating in a thoughtful and prudent manner, could he expected to have anticipated the actual event.3 By that standard, one can make a forceful argument concerning enrollment limits. Teachers can enhance both learning and safety by the efficient use of space, by elminatingstools and other barriers to movement, and by grouping equipment to facilitate free movement in the lahoratory. By having a neat and clean
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' Beny. K. 0. ChemUnify '81 1981. 3(3), 8.
Pine. S. Presented at ACS Safety Workshop. Tacoma. WA 1985. Kennedy,J. F. Presented at ACS Safety Workshop, Tacoma. WA,
1985.
346
Journal of Chemical Education
lahorarory, the reacher e n r t ~ ~ r a p clcauline.as, es nhirh lends tcg safe practice and the re-pecr for safety rules in rhe lab. Laboratow.Eaubment . . This includes all of the materials and chemicals required for an experiment. Most laboratory equipment has evolved to enhance safety. The assumption h i the manufacturer is that the equipment will always be used in the way it was intended. There are some choices that can he made to minimize risk. One of the most obvious is the choice of liquid thermometers. We urge teachers to select organic liquid-filled thermometers when purchasing replacement thermometers. I t is useful to reduce the amount of equipment stored in the student drawer or locker. Most lists of equipment have not been regularly examined for their actual usefulness. We checked our own list against the equipment actually required by the students and found that almost one-third of the items could he returned to the stockroom and placed into general circulation. There are at least three benefits from reducing the amount of equipment assigned to students: (1) there is less chance of breakage or injury; (2) the cost of supporting each student is less; and (3) the chance of misusing equipment is reduced. I t is important, however, to include equipment that students are expected to use on a regular basis (i.e., put a pipet bulb in every drawer if students are expected to use them). Laboratory Experiments Everv instructor has a set of favorite experiments, which may hebased on utilization of local facilities and equipment. Reevaluation must be made when new hazards are identified. Current emphasis on the long-term effects of suspected reagents should encourage every teacher to he prudent and cautious in selectine One should not denend n exueriments. ~ . solely on the authors of a text to justify using a h a z a r k m experiment or reagent. One can choose to do a chloride ion titration with a st3ndnrdized silver iun solution using either ~utnnsiumchromntt. fluoresrrin as the indirator. Whv not choose the latter? Is i t really of major consequence if students do not have the opportunity to see the color of silver chromate? We now determine iron potentiometrically by prereduction with tin(I1) chloride, followed by titration with cerium(IV). The volume of reagent used for iron is the difference between the total volume and that required to reach the tin(I1)-tin(IV) endpoint. Thus, we have eliminated the need for mercurv and dichromate ion in the exneriment. We no longer use potassium dichromate as a primary standard oxidant in general chemistry. Although safety considerations are a major factor in our choice of experiments, one should not choose experiments solely on that criterion. Nor should one expect to make the lahoratory 100%safe. I t is important that students learn to evaluate a situation, to deal with potential chemical hazards, and to develop the correct procedures for dealing with those hazards. We urge that experiments he chosen so that the opportunities for contrdling potential hazards are enhanced. Experiments tried by many students have allowed teachers to reduce risks in most experiments. But the fact that procedures are usually clear does not eliminate the potential hazards. There is one crucial opportunity available to help teachers increase their awareness of possible risks. When a ~
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new experiment is selected for use, the teacher or teaching aid should perform the exepriment before students do it to help identify any potential sources of difficulty or ambiguity. Laboratory Operation (Conduct)
It must he very clear to students that they are dealing with potential hazards and that teachers expect them to learn to handle those hazards in a safe manner. Students must uuderstand safety as a process in which each is intimately involved. While students must understand that the teacher has selected experiments that offer reduced risk, both students and teachers must continue to act in a manner appropriate for the lahoratory situation. A major feature of the student's responsibility is that of good housekeeping. Errors of "accidental" contact will not
happen if theobjects are in their proper places. Spills are less likely if solutions are stored in the proper kinds of containers in the proper storage area. Glassware is less likely to be broken if it is in its proper place. Students must continually work to establish the habits and attitudes required for safe lahoratory work. We urge teachers to consider safety as a process in which both students and teachers become so enmeshed that exercising safety precautions becomes second nature. The process must be so common and so natural that the student and teacher involve a safety consideration at each step of an experiment. Rules may he acceptable for those not yet capable of making decisions for themselves, hut one of the missions of chemical education should be to teach science as process. I t is apropos that the process of risk assessment be made a part of the routine laboratory experience.
Volume 64
Number 4
April 1987
347
