Limestone Products
Why do antacids contain chalk?
The same reaction that sweetens sour soil.
Dr. Lime Explains
Because chalk cancels acid.
Chalk is a soft, fine limestone, and limestone is calcium carbonate. The stomach makes hydrochloric acid. Calcium carbonate neutralises that acid on contact.
The reaction gives off carbon dioxide, which is where the burp comes from.
Worth knowing
This is the same reaction that fizzes in vinegar and the same one that corrects sour farmland. Acid meets calcium carbonate and the acid loses. The scale changes from a tablet to a tonne, but the chemistry does not.
Source: National Institutes of Health, MedlinePlus.
