(inorganic chemistry) An unstable acid, H₂S₂O₂, only known in solution, used as a reducing agent; its salts are hyposulfites).

(organic chemistry) A saturated fatty acid, CH₃(CH₂)₁₅COOH, that occurs only in very small amounts in natural oils and fats

(organic chemistry) An polyunsaturated fatty acid, having 18 carbon atoms and three double bonds, essential for human nutrition; it is found in linseed and other vegetable oils

(chemistry) an anhydrous form of phosphoric acid that exists as a polymeric glassy solid, (HPO₃)ₙ; used as a drying agent and in dental cement

(biochemistry) pyridine-3-carboxylic acid; together with nicotinamide is a part of the vitamin B complex

(organic chemistry) A saturated fatty acid, CH₃(CH₂)₁₂COOH, tetradecanoic acid, found in both animal and vegetable oils and fats; used in the manufacture of soap, cosmetics etc.

(inorganic chemistry) A weak acid, HNO₂, known only in solution, or as its salts and esters, the nitrites; it has a linear structure, H-O-N=O

(obsolete, inorganic chemistry) Hydrochloric acid. / A low grade, industrial grade or impure form of hydrochloric acid, often containing traces of iron.

(chemistry) A supposed acid formed from osmium tetroxide but known only as osmate salts.

(organic chemistry) An unsaturated fatty acid, having 18 carbon atoms and one double bond, found in olive oil and very many other vegetable and animal oils and fats; it is used for making soap, cosmetics etc.