The pure form of phosphoric acid is a white solid at room temperature, but begins to melt and form a viscous, colorless liquid when the temperature reaches 42.35°C. This compound is usually anhydrous at room temperature, meaning it does not contain any moisture. It has a polar molecular structure, however this means it is extremely water soluble.
As a chemical reagent, this acid can often be converted into an aqueous solution. Depending on the amount of acid, it can have a potential hydrogen ion concentration (pH) of 1.08-7.00. 85% phosphoric acid is corrosive but can be rendered non-toxic by dilution.
One of the most common uses of this acid is as a food additive. In Europe, its food additive identification code is E338. It is primarily used to acidify food and beverages, cola beverages being an example. Both Coca-Cola and Pepsi use phosphoric acid to give the drink a slightly sour taste. It is the second most common choice after citric acid due to its low cost of use on a large scale.
Some studies have found a link between phosphoric acid and loss of bone density. A study published in the American Journal of Clinical Nutrition pointed out that women who drank cola every day had a significant loss of bone density. But the results of another study, funded by PepsiCo, claim that a lack of phosphorus in the body can lead to lower bone density. Further investigation revealed that the bone loss was caused by caffeine. A 2001 study based on women found that bone loss in women who drank three cups of Coke a day was related to their substitution of milk, not from consumption of phosphoric acid or caffeine.
This acid has also been linked to kidney stones and chronic kidney disease. Exactly why and whether phosphoric acid is involved is not well understood, although some studies point to cola consumption.
