The diary1 acyl hydrazines of the type ArNCOCH3NHAr have been hitherto little investigated. The only previously known members of this series are mono- acetylhydrazobenzene,'mono-acetylbenzene-hydrazo-ptoluene, 2 and mono-acetylhydrazo- p-toluene.'The acetylation of aromatic hydrazo compounds, by means of which the members of this group may be prepared, was undertaken by us to gain some knowledge of the ...