Organic acid
From eagle-rock.org
Rhubarb stalks contain some oxalic acid
An organic acid is an organic compound with acidic properties. In general, organic acids are weak acids and do not dissociate completely in water. On the other hand, most organic acids are very soluble in organic solvents. Organic acids are used in food preservation because of their effects on bacteria.
A few common examples include: Lactic acid, Acetic acid, Formic acid, Citric acid, Oxalic acid, Uric acid.
