Rosaniline sulphonic acids

The rosaniline dye first obtained was probably a mixture of salts of both para-rosaniline and rosaniline. The names given to it at the beginning, viz., fuchsin and magenta, are still used. Acid fuchsin, a common form of the dye, is a mixture of the sodium salts of the mono-and di-sulphonic acid derivatives of para-rosaniline and rosaniline. 

This salt, unlike those of other sulphonic acids, may be fixed on wool and silk from a slightly alkaline bath. It is probable that the basic groups of rosaniline effect this fixation. The shade obtained is not strong, but on development with dilute acid, whereby the free sulphonic acid is liberated, a good blue shade is obtained. Alkali blue finds its principal application in wool-dyeing. 

Finally, streptomycin can be determined by titrating with a dye formed by coupling diazotizedp-rosaniline with l-naphthol-4-sulphonic acid.< > A sample, containing 1-3 mg of streptomycin, was titrated in 10 ml. of triethylamine citrate buffer at — 0-8 V with a O Ol M solution of the dye. 

The difficulties encountered in the sulphonation of rosaniline are altogether absent in that of the phenylated rosanilines. A monosulphonic acid is formed by the action of concentrated sulphuric acid at a comparatively low temperature, while by a more energetic sulphonation two, three, and even four sulpho-groups may be introduced into the molecule. 

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See also in sourсe #XX -- [ ]

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