Alkalinity vs. High pH
Alkalinity and alkaline (= pH above 7) are not the same. Alkalinity is a measure of the buffering capacity of water – its ability to resist changes in pH. The pH is an indication for the acidity of a substance. It is determined by the number of free hydrogen ions (H+) in a substance. Alkalinity and pH are related to each other as two different measurable parameters of water. In mineralized water, alkalinity rises sharply as pH is raised.
However, alkalinity does not depend strictly on pH. For example, ionized water may have high pH (= alkaline) but has little ability to neutralize acid in the stomach to initiate the production of bicarbonate in the bloodstream. Alkaline ionizer promoters equate acid-neutralizing ability with high pH, but ionized water does not deliver sufficient alkalinity to make a biological difference. On the other hand, Lemon juice is around pH 2 (acidic) but its nutritional matrix provides high alkalinity in body.
Alkalinity is the true measure of acid-neutralizing capacity which includes the bicarbonate (HCO3^-1), carbonate (CO3^-2) and hydroxide (OH^-1) ions. It is measured in mg/l or ppm as CaCO3 (of the amount of acid – e.g., sulfuric acid – needed to bring the water sample to a pH of 4.2).