For the best results this preparation must be carried out rapidly. The vessels and reagents required should be made ready in advance. The oxidizing solution is prepared by dissolving
240 g. (0.89 mole) of ferric chloride hexahydrate in a mixture of
90 cc. of concentrated hydrochloric acid and 200 cc. of water with heating, cooling to room temperature by the addition of 200–300 g. of ice, and filtering the solution by suction.
Eighty grams (0.41 mole) of 1,2-aminonaphthol hydrochloride of a high degree of purity (Note
1) is placed in a
5-l. round-bottomed flask and covered with a solution of
5 cc. of hydrochloric acid in 3 l. of water which has been heated to 35°. The material is dissolved quickly by shaking (one to two minutes), and the solution is filtered rapidly by suction from a trace of residue and transferred to a clean 5-l. flask (Note
2). The oxidizing solution is added all at once while rotating the flask vigorously in order to mix the two solutions thoroughly. The quinone separates at once as a voluminous, microcrystalline, yellow precipitate. The product is collected on a
Büchner funnel, washed well with water (Note
3), and then for more thorough washing it is transferred to a
large beaker, stirred for a few minutes with 2 l. of water (at 30°), and again collected. The filter cake is cut into slices and dried on
filter paper at room temperature in an atmosphere free from acid fumes. The yield is
60–61 g. (
93–94 per cent of the theoretical amount).
The material is pure golden yellow in color and melts with decomposition at
145–147°, with some softening at about 140°. It contains none of the black, sparingly soluble
dinaphthyldiquinhydrone and dissolves without residue in
alcohol or
benzene. Under the microscope it is seen to consist of a mass of well-formed, fine needles. By crystallization from alcohol or
benzene it may be obtained as orange-red needles of good appearance, but the process is unreliable, it involves much loss of material, and the point of decomposition is lowered by 10–20°. It is thus best to use or to preserve the quinone in the form originally obtained; in this condition it is essentially pure and it will keep indefinitely. The material should not be pulverized, for it then becomes highly electrified.