The sixth volume to appear, this is the third devoted to a description of compounds having the naphthalene ring structure. This book includes the hydroxy derivatives of compounds containing one naphthalene nucleus and those naphthols containing halogens, nitro groups, amino groups and azo compounds. This volume includes literature references through 1944 and those references concerned with structure of compounds up to 1950. As in previous volumes, the physiologic properties of the more widely known substances are presented with literature references. Among those substances for which this information is included are 1-naphthol, 2-naphthol, 2-4-dinitro-1-naphthol, orange I, orange II and many others. Menadiol and vitamin K, hydroquinone (dihydrovitamin K) and their numerous derivatives having antihemorrhagic activity are described.