OXIDATION PKODUCTS OF DIANISIDINK. 167 



chloride gave 0.0840 'BaSO^. Sii — 19.0%, lUSO^ — 14./%. 

 CzsHaaO.N, (SO,) requires Sn = 20.4, H^SO, = 16.8%, but the 

 specimen consisted partly of the sulphate of the isomeric base 

 (the polymer) as a result of drying- at too high a temperature. 



5. Bichromate. — This is the dimethoxy-derivative of the so- 

 called " benzidine chromate " investigated by the author,* and 

 like it, is somewhat indefinite, being either quinonoid or quin- 

 hydronic according to circumstances. The specimen analysed 

 was obtained by working at 30 "" and adding an excess of i)otas- 

 siurn dichromate solution to the blood-red mother liquors from 

 the hydrochloride preparation : a voluminous blue slime is ob- 

 tained, which was washed out and dried at 90°. It forms a black 

 violet cake which deflagrates on heating or on touching with con- 

 centrated sulphuric acid. It was therefore analysed i)y boiling 

 with hydrochloric acid and precipitating chromic hydrate. 0.611 

 gave 0.183 Cr..O, = 30.0%. 



■ .C,Hy„0,^^i-^HXr,0_ rccjuires Cr/-);, == 33^r . wliich is 

 sufificiently near to the experimental result for the case of a ct im- 

 pound of this indefinite character. 



P). Iirz'cstigatioii of the broicn isomeric base (polymerised 

 dimethoxy-diphenoquinonediimine). — This is best prepared from 

 undried specimens of the quinhydrone salts by treating with 

 ammonia, filtering and washing with dilute soda ( wlien it becomes 

 rather lighter in colour), and finally with pure water. The 

 product is brick-red on drying, and melts easily, being partly 

 composed of free dianisidine and partly of " poly.nerised dianisi- 

 minoquinone." Titration v\ith Sn.CU used 19% Sn, so that rather 

 less than half is the " quinone." Most of the dianisidine can be 

 extracted by hot 70% alcohol. After this treatment the undis- 

 solved brown substance ( dried at 90° ) used 29% Sn for reduc- 

 tion and melted at 150-175''. Another quantity of gummy im- 

 purity was removed by digestion in acetone and washing. The 

 insoluble dark brick-red melted at 220-240°, and on reduction by 

 stannous chloride used Sn =^ 48.4% of substance : no a^h was 

 left on burning it. 



NH :< >:< >•. NH 



CH3O 0CH3 



or the polvmeric azo-dve formula CgHoyOj^N^ requires 



Sn=4Q.2rc. 



It is fairly soluble in benzene, chloroform and similar 

 solvents. 



A portion was dissolved in hot dilute acid and orecipitated 

 with ammonia, and this procedure repeated until the aqueous 

 filtrate contained no dianisidine (as tested by rendering just acid 

 and adding FeCl,). The "quinone," thus completely freed from 



* Proc. C.S., London I.e., and Trans. R.S.S.Afr. 



