Aniline blue 818 -dyes

Aniline was first isolated in 1826 as a degradation prod uct of indigo a dark blue dye obtained from the West Indian plant Indigofera anil from which the name aniline IS derived... 

A striking feature of disperse dye development in recent decades has been the steady growth in bathochromic azo blue dyes to replace the tinctorially weaker and more costly anthraquinone blues. One approach is represented by heavily nuclei-substituted derivatives of N,N-disubstituted 4-aminoazobenzenes, in which electron donor groups (e.g. 2-acylamino-5-alkoxy) are introduced into the aniline coupler residue and acceptor groups (acetyl, cyano or nitro) into the 2,4,6-positions of the diazo component. A PPP-MO study of the mobility of substituent configurations in such systems demonstrated that coplanarity of the two aryl rings could only be maintained if at least one of the 2,6-substituents was cyano. Thus much commercial research effort was directed towards these more bathochromic o-cyano-substituted dyes. 

Artificial Organic Dyes.—Indigo carmine may be adulterated with artificial organic dyes, especially aniline blue. If silk is dyed with an acidified solution of the carmine and then washed and boiled with water, the fibre will become colourless if the carmine is pure, but remains blue if aniline blue is present. 

In the presence of anions which are precipitated by calcium chloride solution, proceed as follows. Precipitate the acetic acid test solution with calcium chloride solution, and collect the precipitate on a filter or in a centrifuge tube. Remove the water from the precipitate either by drying or by washing with alcohol and ether. Mix a small amount of the precipitate with diphenylamine in a dry micro test-tube, add a little concentrated phosphoric acid, and heat gently over a free flame. Calcium phosphate and free oxalic acid are formed, and the latter condenses with the diphenylamine to aniline blue and colours the hot phosphoric acid blue. The colour disappears on cooling. Dissolve the melt in alcohol, when a blue colouration appears. Pour the alcoholic solution into water thus precipitating the excess of diphenylamine, which is coloured light blue by the adsorption of the dyestuff. The dye may be extracted from aqueous solution by ether. 

Alizarin pure blue dyes a pure blue quite similar to the color of aniline blue (triphenylrosaniline). Its color strength is high and its fight fastness is very good. It is especially valuable for tin phosphate weighted silk with which it is widely used. 

Kirk Othmer l(1947),918(SmalI quanti ties of aniline can be detd colorimetrically by means of a purplish violet color formed on treatment with hypochlorite soln or by conversion of this to a permanent blue dye on treatment with ammonia or phenol... 

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... 

The first acid dye was made by Nicholson in 1862, when he sulphonated aniline blue it was known at that time as Bleu de Lyons (Chapter 1). Other basic dyes were subsequently sulphonated to convert them into acid dyes, making them more easily applicable to wool than the parent basic dyes. Acid Magenta (C.I. acid violet 19), formula (1), is obtained by the sulphonation of magenta ... 

A number of basic dyes, e.g., trypaflavine (H16) and aniline blue (T7), are not excreted in bile, and dyes with a great many sulfonic acid groups (e.g.. Ponceau 6R, azofuchsine V, and azofuchsine N), which are highly hydrophilic, are apparently not excreted by the liver or by the kidney (H18). 

Couplers which form scadet dyes with 4-nitro aniline and red dyes with 2-amino-6-nitrobenzothiazole yield blue dyes with 3-amino-5-nitro-2,l-benzisothiazole [14546-19-1]. 

Mauvein is a base whose sulphate, obtained by mixing cold dilute solutions of potassium dichromate and aniline sulpliate, is a fine, purple dye. A blue dye is also obtained by heating mauvein with aniline. 

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