Fuchsin Acid

Fuchsin acid (Acid magenta) is a red, acid dye of the triphenylmethane series, consisting of the sodium salts of the sulphonic acids of basic fuchsin or of the individual dyes (pararosaniline, rosaniline and new fuchsin), of which the latter is a mixture. The composition of fuchsin acid, like fuchsin basic, can vary with the country of origin and from one manufacturer to another.
Industrial uses of the dye include the colouring of crepe tissues, soap and photographic films and the dyeing of leather, which it penetrates easily.
A 1 % solution of Microme No. 5 in deionized or distilled water (previously adjusted to pH 7-0 with alkali) has a pH of 5-0.
Fuchsin acid is decolorized in solution by the addition of NaOH and in this form it is used as an indicator (known as Andrade's indicator) : this finds application in bacteriology for detecting acid-forming organisms.
Very dilute aqueous solutions of the dye in London tap water (pH about 8-1) fade within two or three seconds. In deionized water they retain their colour considerably longer, however.

dark green crystalline powder

Acid Fuchsin has been used in tissue sections for Masson′s trichrome staining. It has been used as a marker to trace ingestion of solutions by green peach aphids.

Acid Fuchsin sodium salt is used as a pH indicator. It is one of the dyes used in Masson?s Trichome Stain where it is used to distinguish muscle from collagen.

As pH indicator; biological stain.

Acid Fuchsin is mainly used as a diachrome and is part of the connective tissue stains. It also works as a pH indicator.

Not classified

Fuchsin acid has very many applications in biological microtechnique. Gray (1954) describes around two hundred of these.
It was discovered some years ago (MacConaill and Gurr, 1960; Gurr, 1962) that fuchsin acid forms complexes with light green SF (yellowish), conjugation taking place apparently between the amino groups of the first and the sulphonic groups of the second dye. These interactions were first discovered by Professor M .Conaill of University College, Cork, in 1958. About two years later one of these complexes (a blue dye which was given the name of Trifalgic acid; synonyms: MG blue, Falg blue) was synthesized in the solid state by the writer and found useful application in clinical pathology as a differential stain for proteins in electrophoresis (Bodman, 1960).
MacConailPs discovery was made during the course of an investigation into the chemical and physical nature of certain substances present in mammalian tissues and cells. Histological sections were stained first with the red anionic dye, fuchsin acid, then counterstained with the anionic dye, light green SF (yellowish). It was naturally expected that these dyes would impart a dichrome picture, in red and green. However, when he came to examine the sections under the microscope the picture seen was not in red and green but scarlet, various shades of violet and pure blue. The blue coloration excited his interest in particular. Although he considered at first that its presence was probably due to physical causes, subsequent tests carried out by him appeared to suggest that chemical interactions between the red and the green dye had taken place with the formation of at least three new dyes, one of which was blue. Cumulative and circumstantial evidence resulting from histological, physical and chemical experiments, since carried out over a period of years, leave no room for doubt that fuchsin acid and similar anionic dyes which have basic colligators (e.g. primary amino groups), can and do, under appropriate conditions, interact both in vitro and in tissues with other anionic dyes to form compounds which are polyanionic dyes.

Room temperature