Introduction What are Waste Minimization and Pollution Prevention? Why are Waste Minimization and Pollution Prevention Important? Purchasing Chemicals Managing Chemical Inventories Dealing with an Existing Inventory of Unwanted Chemicals Conducting Experiments »Scaling Down Experiments« Substituting Materials Alternatives to Wet Chemistry Reusing and Recycling Chemical Resources Segregating Waste Streams In-Laboratory Treatment of Wastes Working with School Administrators, Students, Other Schools, and the Community Getting More Information Appendix A—Waste Minimization Checklist	Typically, educational experiments are designed at a macroscale level, with little thought about waste minimization. Most macroscale experiments can be easily scaled down and still achieve the same level of analytical rigor. Experimental quantities can be scaled down by about 50% with little effort or cost, or scaled down to 1/100th to 1/1000th of the original quantities using glassware and experiments designed for microexperimentation. The result—less waste, less student exposure, and fewer chemical purchases. In upper-level chemistry courses, microscaling complements the use of analytical equipment such as chromatographs, spectrophotometers, nuclear magnetic resonance systems, etc. These systems require extremely small sample quantities for analysis. Reduced scale chemistry If you cannot convert to true microscale chemistry, try decreasing experimental quantities by a third or half. A 50% reduction in quantities can usually be achieved with conventional glassware. Such scale reductions may require a few trial runs to ensure desired experimental results—a good exercise for students who volunteer for extra credit lab work. (Caution: Instructor supervision is important!) Microscale chemistry Microscale chemistry techniques and equipment can reduce chemical use by as many as three orders of magnitude. Efforts at developing classroom micro experiments for general, organic, inorganic, and physical chemistry courses have been and continue to be successful. Several student and instructor textbooks have been published. Some recommended textbooks are listed in Chapter 15. Two of these books (Ehrenkranz & Mauch, 1993, and Waterman & Thompson, 1993) are specifically intended for high school chemistry classes. Micro techniques are also being explored and developed in radioactive chemistry and radiochemistry. Most microscale techniques can easily be mastered by beginning students, with proper instruction. As an example, conventional experiments with solids use 10- to 50-gram amounts, while microscale experiments can use as little as 25–100 milligrams (mg). Similarly, experiments with liquids can be cut from 25–100 milliliters (mL) to 100–200 microliters (µL). Highly accurate density and specific gravity determinations can be achieved using less than 1 mL of liquid and a micropipette, rather than the conventional larger volumetric flask method, requiring up to 30 mL of the solution. An example microscale experiment: Redox Titration of Manganese Using a graduated or volumetric pipette, place 1.00 (± 0.01) mL of 0.0100M solution into each of three 10-mL flasks. Label as A, B, and C. Acid Solution Titration. Add 1.0 mL of 1M to flask A. Charge a microburet with 0.0200M solution and slowly titrate the permanganate solution drop by drop until the purple color of the solution disappears. Record the volume of added. Neutral Solution Titration. Recharge the microburet with 0.0200M solution. Record initial volume and titrate the solution in flask B. The purple color of permanganate will change to brown suspension of at the endpoint. Record the final volume. Basic Solution Titration. Add 1.0 mL of 1 M NaOH to the permanganate solution in flask C. Recharge the microburet with solution. Record initial volume. Titrate to dark green-colored endpoint of . The remainder of the experimental calculations and exercises are provided in the textbook. (Taken from Szafran, et al., 1993 p. 270)
	Implementing microscale An inexpensive way to achieve an initial level of microscale would be to use flexible, small diameter polyethylene tubing instead of bent glass tubing to transfer gases, using micro pipettes, microburets, and Hirsch filtration funnels rather than the traditional larger size equivalents. (Note: Some of the plasticware may not be suitable for organics.) To fully retrofit a conventional chemistry lab to microscale, some investment is necessary. Full microscale glassware kits cost up to $110 to $150 (advanced levels) per student (1994 prices). Analytical microscale equipment also adds to the initial cost. Typically, one piece of equipment (e.g., one electronic digital balance or one capillary melting point apparatus) suffices for 15 students. These costs are typically recovered in nine months to three years (depending on the size and scope of the program). Chapter 14 provides possible strategies for acquiring funding or equipment to convert to microscale chemistry. The National Microscale Chemistry Center (NMC˛) at Merrimack College in North Andover, Massachusetts, offers free one-week courses in microscale chemistry to educational instructors. Contact the NMC2 at (508) 837-5137 or send e-mail to zszafran@merrimack.edu for more information. Many other colleges are practicing or are converting to microscale experimentation in their laboratories and may offer training or auditing of courses using microscale.
	Microscale equipment Microscale equipment includes (but is not limited to) 96-count well-plates, plastic and glass micro pipettes, microburets, automatic/digital delivery pipettes, microcentrifuge tubes, syringes, glass or plastic inserts to displace liquid volumes in vials and test tubes, and full glassware kits. Analytical equipment may be necessary for performing certain introductory level experiments, and is important for upper-level courses. Analytical microscale equipment includes (but not limited to) an electronic digital balance, capillary melting point apparatus, automatic delivery pipettes and/or syringes, a magnetic stirring hot plate and sand melting baths, and microscale magnetic stirrers. Typically, one of each piece of equipment will suffice for 15 students. New suppliers are continually entering this growing market. Capillary melting point apparatus eliminates the hazards and mess of the traditional oil bath method and determines accurate melting point ranges using only about 1 mg of the sample. A small modification of the process allows determination of boiling points as well. Observation through a magnifying lens allows the student to view the exact temperature at which melting and boiling start. Equipment operation and maintenance are simple and equipment is very durable. The only wastes are small, inexpensive capillary tubes and 1 mg of product. The balance should be a single-pan electronic balance with digital readout, automatic taring, and accuracy to .01, .001, or .0001 gram (depending on the allowable level of error and minimal sample mass used). Automatic delivery pipettes are available in digital or manual micrometer volume settings, and can deliver volumes at high accuracy in varying volume ranges. One delivery pipette with a range of 0-100 mL and one with a range of 100-1000 mL should suffice for each 15 students. This eliminates inaccuracies, wastes, and dirty glassware common with other measuring methods. Not all wastes are eliminated with the delivery pipettes, since the small plastic tips must be changed with each measurement of a different liquid. Syringes may also be useful in measuring microscale quantities. Determining magnetic moments from measurements of magnetic susceptibility of transition metals can be done with very small quantities of product using magnetic balances such as the Evans balance developed by D. F. Evans of Imperial College, or with nuclear magnetic resonance (NMR). These replace traditional methods and require 50 mg or less of sample product.

Return to Title Page

Copyright © 1996 Battelle Seattle Research Center. All rights reserved.