Fuchsin

Fuchsin, an aniline dye (synonyms: rubin, diamantfuchsin, brilliantrubin, cardinal, magenta, grenat). There are basic and acidic forms of F. Basic F. is a mixture of hydrochloric and acetic salts of rosaniline and pararosaniline; the main component of commercial basic fuchsin is hydrochloric rosaniline, forming crystals of varying size with a greenish tint; the acetic salt gives irregular pieces of the same color. F. is poorly soluble in cold water (0.2-0.3%), better in boiling water and ethyl alcohol, and even better in amyl alcohol. Acids such as hydrochloric, nitric, and sulfuric decolorize F. with the formation of a yellow color; caustic soda also decolorizes F. Although F. was introduced into histological technique by Waldeyer, its significance in histological technique is not great—like other basic dyes, it stains nuclei, mucus, the ground substance of cartilage, etc.; its application in bacteriological technique is much broader. Typically, dye solutions are prepared in aniline (according to Löffler) or carbolic (according to Ziehl) water. The recipe for the more commonly used carbolfuchsin of Ziehl: 1.0 g F., 10 cm³ of 96% alcohol and 100 cm³ of 5% carbolic water. Preparations are restained when heated and differentiated with a sulfuric acid solution (10-25%) or nitric acid (15-33%); a 1% solution of hydrochloric acid in 70% alcohol is also used; 96% alcohol and a saturated solution of picric acid are also used. According to the recipe of Baumgarten, histological preparations are stained with a weak solution of F. (8-10 drops of concentrated alcoholic solution per 10 cm³ of water) for 24 hours, rinsed with absolute alcohol, restained with a concentrated aqueous solution of methylene blue for 4-5 minutes; then differentiation with 96% alcohol and mounting in clove oil in Canadian balsam: resting nuclei—blue, mitoses—red. A good stain is obtained according to the method of Ramón y Cajal: 15-20 min. concentrated aqueous (or aniline) solution of F., 95% alcohol until the dye comes off, 5-10 min. solution of 1.0 g of indigo carmine in 300-400 cm³ of saturated aqueous solution of picric acid, then directly 95% alcohol until the sections take on a bluish-greenish color; mounting in balsam: nuclei red, protoplasm yellow, muscles yellowish-green, connective tissue blue. The application of acidic F. (S. Fuchsin, Saurerubin) in histology is much broader—rosaniline-monosodium sulfate or pararosaniline-monosodium sulfate. Acidic F. was introduced into histological practice by Altmann for staining his bioblasts; at present, this dye in various modifications is used to detect cellular chondriome. The most commonly used is the Kull method (see). According to Weigert, acidic F. in the form of a saturated aqueous solution is used for staining myelin with subsequent differentiation with a 1% solution of caustic potash. Kupffer recommends acidic F. for staining neurofibrils in peripheral nerves after fixation with osmic acid. According to van Gieson, acidic F. with picric acid is used for differential staining of muscle and connective tissues (see van Gieson method). Acidic F. is also part of the Ehrlich-Biondi mixture: to 100 cm³ of saturated aqueous solution of orange (brand GMP) is added 20 cm³ of saturated aqueous solution of acidic F. (brand SMP) and to the mixture, with constant shaking, 50 cm³ of methyl green (brand NMP) is slowly added. Thus the basic solution is prepared, which is diluted when used; the indicated dyes can be mixed in dry form and then a saturated solution is made from them, by Fomin.