Over-the-Counter Antacids

Kreidler, Kathy Thornridge High School


Over one-half billion dollars are spent on over-the-counter antacids
every year. An informed consumer will understand how antacids work and
will read the labels to see what ingredients are present. Based on this
information and on a knowledge of side effects, the student consumer
will be able to decide which, if any, antacid to choose.

Apparatus needed: 6 250 ml Erlenmeyer flasks baking soda 6 balloons Tums 600 ml 0.1 M hydrochloric acid Rolaids Alka Seltzer Phillips Milk of Magnesia Maalox tablets methyl orange indicator Recommended strategy: Before class starts, prepare 6 little stomachs. These are 250 ml Erlenmeyer flasks, each containing 100 ml of 0.1 M HCl and a few drops of methyl orange indicator. Put an empty balloon over the mouth of the control flask. Crush one dose of each antacid and place in a balloon. Label the bottom of each flask to correspond to the antacid in the balloon. Place the balloons over the necks of the flasks, but do not allow the antacids to fall into the flasks yet. Tell the students that you have an upset stomach from eating too much pizza last night. Ask what you could take to get relief from indigestion and "sour stomach." Place samples of antacids on the desk. Explain the little stomachs setup. Shake the balloons so the antacids fall into the flasks. Record student observations and explanations on the chalkboard. Pass out a list of ingredients of common antacids. The list could also include the price per dose. Ask what ingredients could neutralize acid and what ingredients could relieve gas pains. Teacher input: Write representative neutralization equations. Explain the action of simethicone. Tell some of the side effects of aspirin, magnesium, aluminum, and sodium salts. Discuss the function of the inactive ingredients. Ask the students to use this new information and their observations to guess which antacid was in each flask. Evaluation: Students work in groups to decide which antacid is the best. Each group shares its decision and the criteria used to arrive at that decision. References: Eby, Denise and Roger Tatum. The Chemistry of Over-the-Counter Drugs.
Unigraph: Seattle, Washington, 1977. pp.14-21.

Graedon, Joe. The People's Pharmacy. St. Martin's Press: New York,
1976. pp.79-90.

Rombauer, Irma S. and Marion Rombauer Becker. The Joy of Cooking.
Bobbs, Merrill: Indianapolis, 1962. p. 557.

Strongin, Herb. Science on a Shoestring. Addison Wesley: Menlo
Park, California, 1985. pp. 41-43.
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