(CAS NO. ) is dried with Na₂SO₄ and vac distd from zinc dust. Also dried by boiling with acetic anhydride, then fractionally distilling. Calvin and Wilmarth cooled redistd quinoline in ice and added enough HCl to form its hydrochloride. Diazotization removed aniline, the diazo compound being broken down by warming the soln to 60 °C. Non-basic impurities were removed by ether extraction. Quinoline was liberated by neutralising the hydrochloride with NaOH, then dried with KOH and fractionally distd at low pressure. Addition of cuprous acetate (7g/L of quinoline) and shaking under hydrogen for 12h at 100 °C removed impurities due to the nitrous acid treatment. Finally the hydrogen was pumped off and the quinoline was distd. 

Other purification procedures depend on conversion to the phosphate (m 159 °C, pptd from MeOH soln, filtered, washed with MeOH, then dried at 55 °C) or the picrate (m 201 °C) which, after crystn were reconverted to the amine. The method using the picrate is as follows: quinoline is added to picric acid dissolved in the minimum volume of 95% EtOH, giving yellow crystals which were washed with EtOH, air-dried and crystd from acetonitrile. These were dissolved in dimethyl sulfoxide (previously dried over 4A molecular sieves) and passed through basic alumina, on which the picric acid is adsorbed. The free base in the effluent is extracted with n-pentane and distd under vacuum. Traces of solvent can be removed by vapour-phase chromatography. The ZnCl₂ and dichromate complexes have also been used.