The very first acid that mankind managed to isolate and use, of course, was acetic acid. And the very term "acid" (from the Latin "acid") probably comes from the Latin "acetum" - vinegar. Violation of technology, in the production of wine by ancient winemakers, led to its souring and the formation of vinegar. At first, it was poured out, but then found use as a seasoning, medicine and solvent.
In 1778, the French chemist Antoine Lavoisier suggested that the acidic properties are due to the presence of oxygen in their composition. This hypothesis turned out to be untenable, since many acids do not contain oxygen, while many oxygen-containing compounds do not exhibit acidic properties. Nevertheless, it was this hypothesis that gave the name to oxygen as a chemical element. It was only in 1833 that the German chemist Justus Liebig defined acid as a hydrogen-containing compound in which hydrogen can be replaced by a metal.
The degree of acidity of a solution is determined by the concentration of hydrogen ions in it, which is usually expressed as the number of gram ions per liter. For convenience, the acidity of solutions is usually expressed in the so-called pH value. Distilled water has a pH = 7, if lower then the solution becomes acidic, and higher - alkaline. Measurements are made on a scale from 0 to 14.
The human stomach is forced to renew its surface every day to replace the damaged one from gastric juice, that is, hydrochloric acid. A person's gastric juice is aggressive enough to completely dissolve a razor blade in a week.
A mixture of two acids nitric and hydrochloric in a ratio of 1 to 3, is a yellow liquid and has a unique ability to dissolve many noble metals (gold, platinum), for which it received the name "Tsarskoy vodka".
Not many people know that phosphoric acid is an important ingredient in the popular Coca-Cola, with an acidity index of pH 2.8.
Formic acid is so named because at the moment of danger it is released by ants to warn other inhabitants of the anthill, and to protect against predators.
In warm-blooded animals, a small amount of lactic acid is produced in the process of metabolism, and its smell allows mosquitoes and other blood-sucking insects to find their victims.
Vitamin C or ascorbic acid has the formula C6H8O6 and is a water-soluble vitamin involved in the biochemical redox processes of the human body.
Citric acid is obtained not only from lemons (25 kg per ton of lemons), but also from the Aspergillus niger mold.