Also known as volumetry, a method of quantitative analysis in chemistry for the quantitative determination of substances in a solution. The name is derived from the Latin-French term "titre" for "fineness". There are various titration techniques. For wine, acid-base titration is used to determine the total amount of titratable acids. This is the sum of the free acids present, excluding carbonic acid. The fact that an acidic and a basic solution completely neutralize each other at a certain ratio is used. The determination of the acid concentration by alkaline solutions is called acidimetry, the determination of the concentration of bases with acids is called alkalimetry. The acids contained in wine are mainly tartaric acid and malic acid, as well as many other smaller quantities. These are chemically very similar. In the wine analysis for the allocation of the official test number for quality wines, the total acidity is determined and shown as tartaric acid in g/l.
The sample must be freed from carbon dioxide before titration. Then a so-called indicator, such as phenolphthalein, is added. At a pH value of 0 to approximately 8.2 dissolved phenolphthalein is colourless; at higher pH values the solution turns reddish-purple; in the strongly alkaline range, at a pH value close to 14 the solution becomes colourless again. This is why the substance is an excellent indicator for the titration of basic solutions such as wine. A lye (base) is then added as titrator in small doses using a burette until an equilibrium between lye and acid(s) is reached. A sodium hydroxide solution is often used for this purpose. At this neutral state (equivalence point) the color change of the indicator occurs. The amount of lye is then measured on the scale of the burette and the amount of acid is calculated. The sulphurous acid and carbon dioxide in the wine are also determined by titration. See also under total extract.
