In a 5-l. flask are placed 1886 g. (11 moles) of phenyl ether (Note 1), 256 g. (8 gram atoms) of sulfur (flowers), and 510 g. (3.8 moles) of anhydrous aluminum chloride. The reactants are mixed well by shaking the flask vigorously; the mixture becomes purple. The flask is fitted with a water-cooled reflux condenser (Note 2) and heated on the steam bath in an efficient hood. The evolution of hydrogen sulfide, vigorous at first, becomes slow after one and one-half hours. After the heating has been continued for a total of four hours, with occasional shaking, the reaction mixture is poured slowly, with stirring, into a 4-l. beaker half filled with ice to which 250 cc. of concentrated hydrochloric acid has been added. More ice is added if necessary. The flask is rinsed with water and the rinsings added to the main product. After the two layers are separated the water layer is discarded and the phenyl ether-phenoxthin layer dried overnight with calcium chloride. This mixture is then distilled at 5 mm. pressure from a 3-l. special Claisen flask having a well-lagged 18-in. column. After removal of the phenyl ether the fraction boiling at 140–160°/5 mm., practically all of which comes over at 150–152°, is collected as phenoxthin (Note 3). The yield is 700 g. (87 per cent of the theoretical amount). This material, which is somewhat colored and has a strong odor, is purified by crystallization from 1.2–1.5 l. of boiling methyl alcohol; the solution should be chilled rapidly and stirred well to prevent the product from separating as an oil. The loss on crystallization is about 3 per cent and the dried material melts at 56–57° (Note 4). A second crystallization gives a product melting about one degree higher.