Science Buddies: "Ask an Expert"

My experiment question is "If the pH of a solution is raised to a higher level (as would an antacid in the stomach), will the enteric coating dissolve and release the drug?" Since enteric coating is made to dissolve in the small intestine (at a higher pH), I will place enteric coated tables in HCl solutions with pH of 1, 4, 6 and 7. What would I use as a control? Normally I would use water but that is my pH 7 solution.

Hi Bridget,

It's good you are thinking about using a control in your experiment. Since the enteric-coated tablets are designed to work in stomach acid, your control would be a pH that is normally found in the stomach. This ranges from pH 1 to 2, or 0.1 to .01 M HCl. Do you have a way to measure pH? If so, you should check the pH of your water. Normally, water will adsorb a small amount of carbon dioxide from the air, so is actually a very dilute solution of carbonic acid about pH 5.5. So you should check the pH of the water. Your experiment should be designed to compare the difference in results between pH 1-2 and the higher pH that would result with antacids. How are you going to measure your results?

Donna Hardy

Thanks. Great information.
Fortunately, we have a water neutralizer because our well water was acidic. It is now tested yearly and is 7. I am going to measure the results by measuring how long it takes to dissolve the enteric coating. I would limit the time to measure to about an hour or two (haven't decided yet) because the protection only needs to last until the stomach empties. Does that sound right?

Hi Bridget,

Your well water is perfect for this experiment! And time is a good unit of measure for a science fair project. Do make sure you do multiple tests for each pH value tested, and plan to include an explanation of pH in your background information. Science fair judges always appreciate an explanation of the science behind a project. You can do a trial run to confirm that 1-2 hours is the right time frame for the experiment.

Donna Hardy

Thank you! I will follow your advice.