Properties | Pure as a colorless powder. Reagents often light red. Insoluble in water, soluble in ethanol, methanol, ether and glacial acetic acid. Alkaline solution was blue, soluble in concentrated sulfuric acid was green. Melting point: 253 ~ 255 ℃ |
Application | Used as acid and alkali indicator, PH value of 6.7 or so when the colorless to orange, PH value of 7.9 or so from orange to blue. Commercially available goods containing impurities were mostly light red, in the PH value of 7.3 to 8.7 from light red to blue and green. |