Eine chem. Verbindung, die in wäßriger Lösung infolge der elektrolyt. Dissoziation Wasserstoff-Ionen u. Säurerest-Ionen liefert u. sauren Geschmack hat. S. bilden mit Metallen, Metalloxiden u. -hydroxiden Salze. Je nach Anzahl der Wasserstoffatome im Molekül spricht man von ein- u. mehrbasischen S.; je nach dem Vorhandensein oder der Abwesenheit von Sauerstoff im Molekül von Sauerstoff-S. oder sauerstoff-freien S. Die Stärke einer S. entpricht dem Grad der Dissoziation, d. h. der Konzentration der Lösung an Wasserstoff-Ionen. Die S. kann u. a. an der Farbreaktion eines Indikators erkannt werden.
Compound that, in solution in an ionizing solvent (usually water), gives rise to hydrogen ions (H+ or protons). In modern chemistry, acids are defined as substances that are proton donors and accept electrons to form ionic bonds. Acids react with bases to form salts, and they act as solvents. Strong acids are corrosive; dilute acids have a sour or sharp taste, although in some organic acids this may be partially masked by other flavor characteristics.
Acids can be detected by using colored indicators such as litmus and methyl orange. The strength of an acid is measured by its hydrogen-ion concentration, indicated by the pH value. Acids are classified as monobasic, dibasic, tribasic, and so forth, according to the number of hydrogen atoms, replaceable by bases, in a molecule. The first known acid was vinegar (ethanoic or acetic acid). Inorganic acids include boric, carbonic, hydrochloric, hydrofluoric, nitric, phosphoric, and sulfuric. Organic acids include acetic, benzoic, citric, formic, lactic, oxalic, and salicylic, as well as complex substances such as nucleic acids and amino acids.
Any of various water-soluble compounds having a sour taste and capable of turning litmus red and reacting with a base to form a salt.
The sharp taste of something acidic (as vinegar or lemon juice); SYN. sour, acidity.