Prepd from β-naphthylamine by diazotization and Sandmeyer CuCl reaction: Scheid, Ber. 34, 1813 (1901); van der Kam, Rec. Trav. Chim. 45, 568 (1926); Hampson, Weissberger, J. Chem. Soc. 1936, 394. By chlorination of gaseous naphthalene at 530° in the presence of iodine, ≈50% of the product being 1-chloronaphthalene which is sepd by fractional freezing: Britton, Reed, US 1917822 (1933).