The oxalate [Beilstein 8 H 326, 13 IV 2279.] is recrystallised from hot water and dried in air. The carbinol is precipitated from the oxalate (1g) in distilled water (100mL) by adding M NaOH (10mL). The precipitate is filtered off, recrystallised from 95% EtOH containing a little dissolved KOH, then washed with ether, and crystallised from pet ether. Dry it in a vacuum at 40o. An acid, almost colourless, solution (2 x 10-5M in 6 x 10-5M H2SO4) rapidly reverts to the coloured dye. [Swain & Hedberg J Am Chem Soc 72 3373 1950, Beilstein 13 H 243, 744.]
