Purification Methods
A neutralised aqueous solution is evaporated to dryness. The residue is extracted into absolute EtOH, evaporated to a small volume and precipitated by addition of absolute Et2O. It is again dissolved in a small volume of absolute EtOH or ethyl acetate and re-precipitated with Et2O. Alternatively, it is purified by adding conc HCl to precipitate the chloride dihydrate. Redissolve in water, neutralise with Na2CO3 and evaporate to dryness. The residue is extracted with CHCl3 and finally crystallised from CH2Cl2 or EtOH by adding Et2O. If the aqueous layer is somewhat turbid treat. it with Celite and filter through filter paper. It can be dehydrated before use in a vacuum. The tetrafluoroborate salt has m 293-295o (needles from MeCN), and the picrate salt has m 203-204o (from EtOH). [Blicke et al. J Am Chem Soc 57 702 1935, Duke & Brown J Am Chem Soc 76 1443 1954, Popov & Humphrey J Am Chem Soc 81 2043 1959, Singhal & Raj Synth Inorg Met-org Chem 23 1011 1993, Beilstein 16 III 1006, 16 IV 1170.] POISONOUS.
