( '•^7'/ ) 



Chemistry. ''licuzidliie Inins/ornKtlloH.^' \\\ Dr. J. Pottkk van 



Loon (( Ji'oiiiiiucii). (( "oiiiiimiiicalcd hv I^i-of. ( '. A. I.obrv dk 

 Urivn). 



((lomiiiiiiucalcd in llio mcoliiiii,' (if Novijiiiltcr 2'.t, 1002), 



It is known llial livdrazohcn/cnc wIkmi IrcaUMl wilh a dilnlc mineral 

 acid is conN-crtcd inio hcn/idinc and diplicnvlcnc, Ucnzidiiic liciiin', 

 liowcvcM-, llic main prodncl. I cndcaxonrcd lo ascci-laiii llic proporlion 

 ill which the isoiiKM-s arc loniicd and in how far this depends on ihc 

 teniperatnre and the concentration of the acid and I further attempted 

 to measure the \(docity with wJiich the transformalion takes |)lace 

 under definite circumstances. 



l>en/i(nne \n as obtained pure hv recrvstalHsation from water and 

 (hstiUation in \acno ; the ineltinu' point of this siihstance was TiS" 

 which is in aiirecMiient with the stateinenls of iAIkkz and Stkasskk. 

 (Joiirn. f. Pract. V\\. N. V. (iO. LSI)). 



For the preparation of liy(h-azol>eii/eJie, azohen/eiie was used as 

 the startinu' point : this was purified by distillatioji and then rechiced 

 witli zinc (hist in an alcoliolic alkaline sobition. The hvdrazobenzene so 

 obtained was dissolve*! by warming- iji alcohol and the still \('llow 

 li(pii(l decolorised by means of ammonia and zinc dust : the (illrale 

 deposited pure white crystals of hydrazobenzene which could be 

 s(>parated unallercMl from the licpiid. A determiiiation of the melting- 

 point ,uave as residt 122^. 



For the study of the transformation it was necessary to have a 

 method for the (pianlitative determination of benzidine. It was found 

 |»ossible to do this lii-avimelrically by addiiiii' |)otassinin sulphate to 

 a solution contaiuinii- not too much free acid and so preci|)italinii' the 

 base as sul[)hate w liich was then collected on a weighed filter. Accordiii<i: 

 to my ex|)eriments, the sliuht solubility of benzidine sul|)hate amounts 

 to 5 () milliuranis |)er 100 cc. of \\ater at the (U'diuary temperature 

 and conse(piently a correction should be applied. To ascertain in 

 what proportion the two bases are formed durinii- the transformalion 

 of' hydrazobenzene, wcij^hed (piantities of this substance were put 

 into bottles of about 120 cc. capacity and then shakcMi with a definite 

 solution of an acid until all had dissoKcd. The benzidine present 

 in the solutio]i was then estimated, as directed, and the proportion 

 calculated from the two data. 



At the ordinary tem])erature, A710 hydrochloric acid used in this 

 maimer causes 84 per cent of the liydraz(»benzeue to be converted 

 into benzitline. Normal li\ (Irochloric, In (Iroliromic acids con^■ert *M) 



