Über den Verteilungssatz der Auxochrome bei Azokörpern, II Dihydroxy‐azobenzole

The validity of the rule of repartition of the auxochromes is examined for dihydroxy‐azo and dihydroxy‐4′‐nitro‐azo compounds with hydroxy groups in 2,4‐, 3,4‐ and 2,5‐position. In conformity with the rule the absorption maximum of the 2, 5‐dihydroxy‐azobenzene is situated at a considerably longer wave length than the maximum of 2,4‐dihydroxy‐azobenzene. The 3, 4‐isomer with its absorption maximum at a relatively short wave‐length seems to contradict the rule. On the other hand all alkali salts of both series conform to the rule of repartition in an impressive way.