Bromothymol Surprise SUBMITTED BY
Linda L. Maler Bucklngham Browm 6 NIcIwIs School Cambrldge. MA 02188
CHECKED BY
Galen P. Me11 Unlvewlty 01 Montana MIasouIa, MT 59812
Bromothymol blue surprise is a quick demonstration used t o illustrate the acid-base reaction of a common indicator. The shift in color is dramatic and readily visible in a classroom. As the carbon dioxide gas evolves, the color changes in correlation with the percent of acidity in the solution.
Materials
100-mLgraduated cylinder 50 mL bromothymol blue (0.01%soh.)
Alka Seltzer tablet Procedure
Fill the graduate with 50 mL of bromothymol blue solution. Drop in one tablet of Alka Seltzer. Initially, the blue solution will turn yellow because of the lame amount of carbon dioxide pas released: slowlv the solution will turn green and begin to foam up &d o i t over the edges of the graduated cylinder. The color change to green is caused by the evolution of carbon dioxide gas. A slight variation would be to chill the bromothymol blue solution, and the reaction will take place more slowly.
Volume 67
Number 11
November 1990
063
