On the Production of Single Crystals of Naphthalene and Anthracene

Furnaces for the growth of naphthalene (m.p. 80 °C.) and anthracene (m.p. 217 °C.) crystals from the melt by the Bridgman method are described and discussed. The advantages of long furnaces are emphasized. A seeding technique may be used to produce long crystals, and has been successful in producing naphthalene crystals [Formula: see text] feet long. A technique for polishing the crystals which gives flat, smooth surfaces is described. Methods of determining the orientation of the crystals by cleavage and by examination of the isogyres or birefringence in a polarizing microscope are given. A simple method for producing anthracene crystals by recrystallization from solution in N,N-dimethylformamide is given, and apparatus for producing very thin sublimation crystals of anthracene is described. The procedures may also be employed to produce mixed crystals.