Microscale

Three Professors Change how Chemistry is Taught

Tamara, Tam to her friends, sits on a stool in her organic chemistry lab. Other students enter the lab; their rubber boots wet from what seems like endless days of April rain, squeak on the tile floor, the sound echoing off the brick and steel walls. April showers - still waiting for the flowers. Spring in New England. Tam’s lab partner sits next to her and pulls mimeographed sheets of paper from her backpack. She places the papers on the black stone counter, trying to keep the papers dry as she removes them from the wet bag.

Tam and her partner examine the glassware before them: tiny beakers, graduated cylinders, glass tubing held on adjustable racks. A small Bunsen burner waits, unlit, a few inches away. They compare notes and double-check that they have properly assembled everything for the day’s exercise. They review the list of chemicals they will be using for the lab, seeing among them benzene, to be handled only beneath a ventilation hood. A dozen other student pairs do the same. A low hum of conversation fills the room.

Benzene is a naturally-occurring chemical consisting of six carbon atoms. It is present in hundreds of chemicals we use every day, from gasoline to paints. It evaporates in the air and has a sweet odor, which is detectable at very low concentrations.

Tam, like thousands of college sophomores across the country prepares for her two-hour organic chemistry lab. But unlike others, she, her lab partner, and the others in the Bowdoin College classroom are the first in the country, indeed in the world, to be taught chemistry using microscale chemistry techniques.

Microscale was the brainchild of three college chemistry professors: Sam Butcher and Dana Mayo from Bowdoin, and Ron Pike from Merrimack. In the early 1980s, the professors suspected that the manner in which organic chemistry had always been taught was unhealthy. Butcher, Mayo, and Pike watched students heat, filter, pour and weigh chemicals in their labs and wondered whether the way they worked with these chemicals was safe. Students wore gloves and took care to assure that the chemicals did not get onto the skin or into their eyes or mouths, this was a matter of teaching good laboratory technique, but the professors had concerns about the air the students and the staff breathed.

In the early 1900s, benzene was used in the manufacture of everything from bicycle tires to paints to hats. But by the late 1920s, researchers knew of its harmful health effects at concentrations as low as 200 parts per million in air (0.02%). One ppm is one grain in half a cup of salt.

The three professors made some rough calculations and tallied the chemicals used in the lab. Focusing on the most harmful chemicals, they determined the quantity of chemicals used over the course of a semester. This was relatively easy, as they knew how many gallons of chemicals they had to buy each year to keep the stockroom fully stocked. Butcher, an air chemist, calculated how much of each chemical evaporated into the air from all the heating, pouring, weighing, and filtering during all of these experiments. From this, they came up with an estimate of the concentration of the chemicals in the lab’s air. They found that too often the concentration of chemicals was hundreds or thousands of times higher in the laboratory air than the amount they considered safe. Mayo and Butcher concluded that the ventilation in the labs at their college was woefully insufficient.

The solution was either to multiply the lab’s ventilation by 100 to 1000, maybe complete the entire lab under a big fume hood, or decrease chemical usage by that same amount. Mayo, Butcher, and Pike decided that the best approach was to rethink organic chemistry lab experiments with an eye toward reducing chemical use to volumes previously considered totally impractical.

By 1939, researchers had linked benzene to leukemia at concentrations as low as 25 parts per million.

If chemistry is like baking, and if completing an organic chemistry experiment is like following a recipe, imagine the challenge of dividing everything into a thousand parts. Two cups of flour becomes a tenth of a teaspoon. How do you divide an egg into 1000 equal parts? How do you mix batter when it all fits inside a thimble? How long do you bake it? The same principle applied to chemistry labs. The big beakers and burners used to heat liters of liquid were fine for heating large volumes, but how would they slowly heat a teaspoon of chemicals?

Mayo and Pike got to work rewriting the cookbook for organic chemistry instruction. They made glassware specifically designed for use with ultra-small volumes of liquid. They spent nights redesigning experiments and then testing them in their lab with upper-level students and other teaching assistants. Satisfied that the experiment was working, they set to writing these labs out for students, listing their recipes and then testing them out. Rewriting and retesting. Finally, they gave the recipes to their students and hoped they could replicate the work.

In 1977, OSHA reduced the Permissable Exposure Limit (PEL) of benzene to 1 ppm.

Back in the chemistry lab, Tam holds her head in her hand, her elbow on the counter. She goes over the sheaf of pages for the fourth time, reading the instructions, looking at the beakers, rereading the instructions, walking herself through the experiment, measuring, heating, dissolving, rinsing, weighing. The use of benzene, even in tiny amounts, is intimidating. Tam doesn’t want to mess it up.

What Tam probably does not appreciate is that she is on the cutting edge. In the years that follow, the microscale concept will quickly take hold in college chemistry labs as schools across the country learn that microscale creates a safer environment for their students. An added benefit is that colleges significantly reduce the cost of disposing of all of the chemical waste: since microscale involves the use of such small quantities, the amount of leftover chemicals that must ultimately be disposed is also reduced. Some estimate that up to 40 percent of colleges in the U.S. now use microscale.

What started as an idea with three college chemistry professors changed the way college chemistry is taught.