Blue, Alkali Aniline

The new aniline dye companies in Europe displayed their wares at the 1862 London International Exhibition, where Hofmann, as juror, acquired a number of samples. They included a blue (7) discovered, almost by chance, by two French chemists working near London in 1861. It had first appeared when excess aniline was erroneously added to the aniline red reaction mixture. E. C. Nicholson in 1862 treated the aniline blue with sulfuric acid to yield a more valuable product, the soluble alkali blue, later better known as Cl [Colour Index] Pigment Blue 61. In May 1863, Hofmann found that the aniline blue was a substitution product of aniline red in which three phenyl groups had replaced three hydrogens (Scheme 2). This immediately suggested that other substituted derivatives might be made and perhaps even provide new aniline dyes. Alkylation with ethyl iodide showed that this was indeed correct. Hofmann achieved stepwise replacement of three hydrogens to afford colorants that were, successively, reddish violet, violet blue and then violet, what were soon known as the Hofmann s violets (8). Hofmann next turned to the aniline red process, and found that the colorant was formed not from aniline alone... 

Diamido-triphenylmethane — CH,(C Hs)(CgH4,N H])3— is produced by the action of anilin chlorid and benzoic aldehyde upon each other in the presence of ZnClj. The salts of this base are blue, and are decomposed by alkalies with liberation of the base, which is a yellow, imperfectly crystalline solid, insoluble in water, soluble in benzene and in alcohol. 

Eurukawa and co-workers [81] state that PANI is an interesting material because it is not only an ECP but is also a good material to use as an electrode of a secondary battery with aqueous or non-aqueous electrolytes. PANI polymerised from aniline in an aqueous acid solution is converted to several forms with different electrical properties by acid/base treatments and oxidation/reduction. The as-polymerised form gives high electrical conductivity ( 5 S/cm). It becomes insulating when treated with an aqueous alkaline solution or is reduced electrochemically in an aqneons acid solution. Reduced-alkali-treated PANI is also insulating and is unstable in air its colour changes from white to blue upon exposure to air. PANI doped with electrolyte anions is obtained by electrochemical oxidation [82]. It was found in this work to be a new conductivity form (o = 5.8 S/cm). Recently, a secondary lithium battery with a reduced alkali pellet as the cathode, and non-aqueous electrolytes has been developed as a power source of memory back up and a maintenance-free power source combined with a solar battery. 

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