edited by G. WOOD CLAIRE Eastern Wine Technical College 354 Hogan Road Bangor. ME 04401
Microchemistry Clelr G. Wood Eastern Maine Technical College 354HcganRoad BBngor. ME 04401 A significant change is taking place in today's chemistry laboratorv. This is the steadv increase in adoption of the microchemical laboratory conEept at secondary and postsecondary educational institutions across the country ( I ) . The microehemical approach is being adopted to heip solve a number of problems that beset today's cbemistry teacher.
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Disposal costa per package for smaller units are usually only 1520% that of larger units. Risk of accident,hreaksge, and exposure is less when handling the smaller package sizes. Storeroom requirements are greatly reduced. The large "economy size" often requires a need for additional equipment such as secondary containers, funnels, pumps, and labels as well as personal protective equipment. When problems of storage, handling, and disposal are taken into account, material dispensed from the "economical size" can be 50%more costly than that drawn from the smaller package.
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By utilizing the microchemical approach, teachers can purchase small package sizes and still maintain sufficient inventory for several years of stable or nontoxic chemicals. For hazardous chemicals, or those with poor shelf life, only a I-year supply should be maintained.
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Safety Student and instructor safety increases when the amounts of reaeent used is lessened. Phifer and Matthews lints six of the most common reasons for accidents in the chemistry lab (4). Soills from a droooed. container. .. . broken,. or tiooed-over .. C& from broken elassware or reagent containers. The authors point out that if a 1 -I. container is dropped on the floor, there is a virtual certainty it will hresk. Tests with a l-ozhottleshow there is only a 1% probability of breakage under similar circumstances. Escape of vapors or gases from the reaction. The reaction getting out of hand. Unsafe storage or handling of chemicals. ' Unsafe or improper disposal of chemicals.
In today's litigious society the chances aregood that any laboratory accident involving injury will result in the teacher being involved in a lawsuit. Federal OSHA and many states have enacted stringent Chem LD. or "right-to-know" laws that present new problems for storage and use of larger quantities of chemicals. Disposal of surplus, aged, and waste chemicals is becoming increasingly difficult and expensive.
One response to these problems has been to replace much of the laboratory proEram with videotapes, computer simulations. and demonstrations. For those who believe the students should still get their "feet wet" in the laboratory, the microchemical approach offers an attractive alternative. Mauch offers these advantages in adopting the microchemical approach in the high school cbemistry course (2). "Micro" amounts of chemicals orovide a auanturn leao in the safe manipulation of putenrially hazardous chemicals while, at the name time, the curt of operating the program is rut. Required storage space for equipment and chemicals is greatly reduced. Many experiments can he shortened to one period allowing for a greater "umber and variety of labs to he done. Many labs are not equipped with fume hoods, eye-wash stations, drenching showers. and other neeessan, safetv Micro.eauioment. .. chemistry experiments can be safely done in any room in the ~
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Many experiments that have been abandoned by teachers aa unsafe can he safely don? in microscale. An example is the explosion of hydrogen and oxygen mixtures.
Economics Historically teachers have purchased larger quantities of chemicals because of the orice reduction. One maior chemical supplier, for example; sells sodium hydroxide for $3.50 per 100 g or $35.00 per kilogram. A kilogram bottle, on the other hand, costs only $19.00 and represents a significant saving--or does it? Consider storage and shelf life. A larger bottle takes up more stockroom space and is seldom used up during the course of a year. Often new reagents are bought for the coming year and the old bottle gets pushed to the back of the shelf. How many have opened fresh bottles of sodium hvdroxide while half-filled bottles of vellets. elued into a n intractable mass by atmospheric moistire, sit'& the shelf? Stockrooms become the eravevards of oartiallv emotied containers whose contents have either butlived their shelf life or are no longer used in the curriculum. The ACS pamphlet "Less is Better" offers these reasons for buying only those quantities of chemicals that can be used in a year (3). 596
Journal of Chemical Education
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Preparing small volumes of solutions, particularly those that eenerate heat. fumes. and eases. oresents fewer oooortunilies for accidents as does tKe handling of apparatus such as templates used in olace of test tubes. The potential for fire andkxplosion is reduced, and there is less dkmand placed on the hoods or ventilation system. Picture the difference hetween putting 5 drops of concentrated sulfuric acid from a 1oz dropper bottle into a template depression and pouring 5 mL from a 100-mL graduated cylinder into a test tube, and the potential for increased safety is obvious. Aside from student safetv. adovtine the microchemical approach will reduce chances of 'accildent in storage and disposal of chemicals. Jay A. Young lists old, partially filled bottles, long unused and often with no labels, as the most common oroblem of stockrooms (5).Because of inadeauate space, incompatible chemicals &stored adjacent to kach other, containers are stacked in the aisles or on too of each other; and flammables do not have adequate ventilation. Frequently schools do not have either a corrosives or a flammables cabinet, and jugs of acids or cans of solvents may be found stored in inadequate stockrooms or even laboratory aisles. Resources There are several resources currently available to help the ~. o r o a c hRusso . bas writteacher to adoot a microchemical a . ten a laboratory manual with microscale experiments covering all the topics normally found in the high school curriculum (6).The preface contains a helpful introduction to microchemical apparatus, such as templates and dieposahle pipets, and explains the drops versus milliliters concept. A
manual by Mills and Hampton is similar in format with the choice of experiments differing in some respects (7). A set of five computer disks, containing over 80 microscaled experiments for general chemistry, is obtainable from John Mauch of the Microchemistry Workshop (2). The experiments are also available in printed format. Mayo e t al. of Bowdoin College have pioneered in reducing organic laboratory exThis has resulted in the publi~ e r i m e n tto s microscale (8.9). cation of a newsletter, ~ k a l l e rIs Better, and numerous workshops in microorganic chemistry offered every summer ( I ) . A comprehensive microscale organic laboratory manual has recently appeared by Pavia e t al. (10). The following are companies known to the author to supply apparatus and reagents for microscafe experimentation. 1. Flinn Scientific Ine., P. 0.Box 219, Batavia, IL, 60510. (312) 8796900 2. Fisher Scientific,Educational Materials Division, 4901 West LeMoyne St., Chicago, IL 60651. (800) 621-4169 3. Lah-Aids Inc., 249 Trade Zone Drive, Ronkonkoma, NY 11179. (516) 737-1133 4. Thomas Scientific, 99 High Hill Rotary, Swedesboro, NJ 08085. (800) 345-2103 5. Chem Service, Inc., P. 0. Box 3108, West Chester, PA 19381. (215) 692-3026 6. Kontes. P. 0. Box 129. Vineland. NJ 08360. (800) 223-1150
Demonstrations involving the microchemiesl approach are starting to appear in the literature. Epp et al. recently described a
microscale method of illustrating Graham's law of gaseous diffusion utilizing the bottom of a tissue culture plate and a sheet of clear acetate (11).The classical demonstration of Graham's law unusually .involves .. .~ . the insertion of cotton wads soaked in hvdrochlorie acid and ammonia solution, respectively. into opposite ends of a glass tube. Epp's method nut only removes the harards of gaseous hydrogen chloride and ammonia in the room but has the added advantage being demonstrated on an overhead projector. You owe it to yourself and your students to obtain copies of these new texts and the catalogs and see for yourself if the microchemical approach will increase safety and reduce expenses while maintaining teaching effectiveness. ~~~~
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Literature Cited 1. Maya, D. W.: Pike, R. M. SmolleiIs Botler: The Newslettar o/Micmscok Orgonie Chemistry, 1988.2(2).Available at modest cost from the Depl. of Chemistry, Bowdoin College, Brunsuick, ME 04011. 2. ~aueh. J. ~ i c r o c h ~ m i s t workrhoir: rv ~ i e rM o O I scientific: ~ ~ s s e oWA, , 1988. 3. Less I; Bsttrr ~ ~ b ~ h~ ~ m~ i Manogernent ~ ~b l t ~ /or &Waste Reduction: American Chemical Society: Washington, 1985. I. Phifer. L.: Matthew, C. Am. Lob. 1918 (Augua1).81-85. 5. Young, J. Irnpravinp Sa/ety in the Chemical Lobomlory A Raefkol Guids Wiley: New York, 1987: pp 206.107. 6. Russo, T. Mierochemistiy /or High Sehaol General Chemistry: Kemtee Educational Corporation: West Chestcr. OH. 1986. 7. Mills. J.; Hampfon. M. Mieroscok Lobomtory Manual for General Chemirtry; Randam House: NeuYork. 1988 8. Mayo. 0. W.; Butcher, S. s.:Mayo, D. w.: Pike, R. M.; Fwfe, C. M.: H0tham.J. R ; Page, D. S. J. Chem Educ. 1985,62.147-148. 9. Msyo. D. W.; Butcher. S. S.; Pike. R. M.: Fmte, C. M.: Hofham, J. R.; Pape, D. S. J. o h - PA,,,. ."-"," ,a% m-,.." ,*Q.,S, " 10. Psvia, D.: Lsmpman, G.: Kriz, G.: Engel, R. Introduction to Orgonk Chemistry ~ o b o r o i o r y~ e c h n i g u e s ~: ~i e r o a c o~i ~ ~sa~nders: ~ ~ l l e n t o ~w nPA, , 198s. ~ n. Epp,D.: Lyons,E.: ~ r o o k s , DJ. . Chem. Edur. 1989.66.436.
Volume 67
Number 7
July 1990
597
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