When you are mixing hydrochloric acid with water to create simulated stomach acid, what is the accurate pH?
The secretions from the wall of the stomach have a pH of between 0.8 and 1. This is a very corrosive level of acidity which would normally destroy tissue cells. Although the stomach wall is protected by a layer of mucus that prevents contact with the cells themselves, it would be a little risky to have that level of acidity persisting continually in the stomach. In practice, during digestion, the stomach will contain liquids ingested by mouth. It will also have other substances such as proteins which buffer the acidity at a higher level. These factors will reduce the actually average acidity to around pH 2 -4 depending on how much additional water and other stomach contents have been ingested. I would use a pH of 2 -4 , say 3, as being the normal average pH or maybe 2 if you want to simulate the conditions at the very start of the digestive process. Take care using concentrated HCl !!!
