methyl orange
Chemistry
noun
An orange crystalline dye that is the sodium salt of the azo compound of dimethylaniline and sulphanilic acid and is chiefly used as an acid–base indicator, changing from red to yellow-orange over a pH range of 3.1 to 4.4; (CH3)2NC6H4NNC6H4SO3Na.
Origin
Late 19th century.