The pH scale measures the acidity or basicity of a liquid solution, ranging from 0 to 14. A value of 7 represents a neutral substance, like pure water. Solutions below 7 are acidic, while those above 7 are basic, or alkaline. Because the scale is logarithmic, a change of just one whole number represents a tenfold difference in the concentration of hydrogen ions. Cola, like many other soft drinks, is known to be highly acidic.
The Measured Acidity of Cola
Major cola brands exhibit a pH typically falling within the range of 2.3 to 3.5. This range places these beverages firmly in the highly acidic category. The acidity of cola is comparable to common household liquids such as lemon juice (1.8 to 2.4) and vinegar (2.4 to 3.4). The distinct tartness in the flavor profile of cola is a direct result of this high acidity, although the substantial amount of added sugar often masks the sour taste.
The Source of Acidity in Cola
The acidity of cola is primarily due to the addition of specific compounds during manufacturing. The main contributor is phosphoric acid (\(H_3PO_4\)), which is added to enhance flavor with a sharp, tart note and to act as a preservative. This acid is a strong acidulant, meaning it readily releases hydrogen ions into the solution, driving the pH down significantly. A secondary source of acidity comes from the carbonation process itself. Dissolving pressurized carbon dioxide gas (\(CO_2\)) into the liquid creates carbonic acid (\(H_2CO_3\)). While carbonic acid is a weaker acid compared to phosphoric acid, it still contributes to the overall drop in pH.
Impact on Dental Enamel
The low pH of cola presents a direct challenge to the protective layer of the tooth, known as dental enamel. Enamel is primarily composed of the mineral hydroxyapatite, which begins to dissolve in a process called demineralization when the surrounding environment becomes too acidic. The critical pH threshold for enamel is around 5.5; any pH below this point causes minerals, specifically calcium and phosphate, to leach out of the tooth structure. Since the pH of cola is significantly lower than this critical threshold, exposure causes an immediate softening of the tooth surface. Frequent consumption or prolonged contact greatly exacerbates this erosive effect. The softened enamel also becomes highly susceptible to physical wear from brushing or chewing soon after drinking.
Acidity and the Digestive System
When cola is consumed, the acidic liquid enters the stomach, which is already a highly acidic environment. The stomach naturally produces hydrochloric acid, which gives it a baseline pH ranging from approximately 1.5 to 3.5. The acidity of cola (2.3 to 3.5) is often within or even milder than the normal acidity the stomach is designed to handle. The stomach lining is protected from its own potent acid by a thick layer of mucus, making it resilient to the acid in cola. Once the acidic mixture passes into the small intestine, the body employs strong buffering systems, primarily using bicarbonate, to rapidly neutralize the acid. This neutralization is necessary because the small intestine is not equipped to handle the low pH. The digestive system efficiently manages the acid load from a cola without disruption.