Standard reagent bottle, 20th century.
© Science Museum / Science & Society Picture Library
Reagent bottle with a ground glas stopper and sand blasted label reading 'acetic acid'. A reagent is a substance or mixture used in chemical analysis. Many laboratory chemicals are stored in this type of bottle. Acetic (or ethanoic) acid (C2H5OH) is one of the simplest organic acids. Vinegar contains 5% or more ethanoic acid, which is produced by fermentation.