To 450 cc. of concentrated hydrochloric acid (sp. gr. 1.19) and 500 cc. of water, in a 4-l. (1-gal.) earthenware crock equipped with an efficient stirrer, is added 143 g. (1 mole) of β-naphthylamine. The suspension of the amine hydrochloride is cooled by the addition of 500 g. of cracked ice. When the temperature reaches 5°, solid sodium nitrite (about 69 g.) is added until starch-iodide paper shows an excess. During the diazotization about 600 g. of cracked ice is introduced at such a rate as to keep the temperature at 5°. The cold solution of the diazonium salt is filtered to remove a small amount of precipitate and returned to the crock. A solution of 271 g. (1 mole) of mercuric chloride in 300 cc. of concentrated hydrochloric acid is mixed with 300 g. of ice and added slowly to the rapidly stirred solution. A heavy precipitate of the yellow addition compound of β-naphthalenediazonium chloride and mercuric chloride separates. Stirring is continued for a half hour, after which the precipitate is collected on a 20-cm. Büchner funnel, sucked as dry as possible, and washed with two 400-cc. portions of water and two 150-cc. portions of acetone (Note 1). The solid is air-dried at about 20° (Note 2) to constant weight. The yield is 380–390 g. (82–84 per cent of the theoretical amount) (Note 3).

In a 2-l. round-bottomed Pyrex flask equipped with a stirrer are placed 139 g. (0.3 mole) of the addition compound, 700 cc. of acetone (Note 4), and 38 g. (0.6 gram atom) of copper powder (Note 5). The mixture is cooled at once to about 20°, stirred for one hour, and then allowed to stand overnight. The insoluble material is collected on a Büchner funnel (Note 6). The solid mixture is extracted with about 3 l. of boiling commercial xylene and filtered through a hot funnel. On cooling the filtrate, crystals of β-naphthylmercuric chloride separate (Note 7). The yield of product which melts at 266–267° is 52–64 g. (40–49 per cent of the theoretical amount based on the amine used) (Note 8) and (Note 9).