Summary By reduction of 3, 3'-dinitro-4, 4'-dihydroxy-azobenzene to the corresponding diamino-dihydroxy-azobenzene, and by subsequent condensation with formaldehyde and sodium bisulfite, N, N'-dimethylenesulfurous acid-3, 3'-diamino-4, 4'-dihydroxy-azobenzene has been prepared. Owing to extreme susceptibility of the intermediate diamino compound to oxidation, it is impracticable to attempt to isolate it, and the entire process is carried out ...
