What is the acid in your stomach

Its hydrochloric acid (H Cl) with the pH value of 1.

1. Stomach acid is hydrochloric acid at a pH of 1, which means that it is at a concentration of 0.1 moles/liter.
2. When something is swallowed, it reaches the stomach within seconds.
3. Stomach acid does not dissolve enteric coatings. That's the whole point of an enteric coating; it doesn't break down until the small intestine. In fact, there's a really interesting picture in a recent New England Journal of Medicine of an enteric-coated aspirin lodged in a stomach ulcer. The coating was perfectly intact, so that you could still read the printing on it.
   
   

The photo to the right shows a Theralac^® capsule before (top) and after (bottom) 90 minutes in stomach acid at pH 1.6. The outer cellulose Vegicap^® has dissolved and a protective gel has formed in the approximate shape of the original capsule, the red color is from the grape skin extract which acts as a protective buffer.