568-02-5

Violet crystals. Insoluble in water, soluble in glacial acetic acid and hot benzene.

As indicator in saturated alcoholic solution. pH: pink 0.0 to yellow 1.6; yellow 6.0 to green 7.6.

ChEBI: An organic heterotetracyclic compound that is naphtho[2,3-f]quinoline-7,12-dione carrying two additional hydroxy groups at positions 5 and 6. Used as an acid-base indicator. Between pH 0.0 and pH 1.6 it changes from pink to yellow, and between pH 6.0 and pH 7.6 it changes from yellow to green.