CHAPTER XVIII 

 METHYLEN BLUE 



376. Methylen Blue is a " basic " dye, being the chloride or the 

 zinc chloride double salt of tetramethylthionin. It appears some 

 persons have confounded it with the " acid " dye methyl blue, 

 to which it has not, histologically, any resemblance. 



Commercial methylen blue sometimes contains as an impurity 

 a small quantity of a reddish dye, which used to be taken to be 

 methylen red. This impurity is present from the beginning in 

 many brands of methylen blue, is frequently developed in solu- 

 tions of the dye that have been long kept (so called " ripened " 

 solutions), and is still more frequently found in kept alkaline 

 solutions. According to Nocht (Centralb. BakterioL, xxv, 1899, 

 pp. 764—769 ; Zeit. wiss. Mik., xvi, 1899, p. 225) it is not methylen 

 red, nor methylen violet either, but a new colour, for which Nocht 

 proposes the name " Roth aus Methylenblau." 



Conn (op. cit.) says : " Methylen blue BX, B, BG, BB : grade 

 preferred for biological work, Methylen blue U.S.P. Solubility at 

 26° C, in water 3-55 per cent., in alcohol 1-48 per cent. The dye is 

 theoretically tetra-methy 1-thionin ." 



According to Mich^lis (Centralb. BakterioL, xxix, 1901, p. 763, 

 and XXX, 1901, p. 626 ; Zeit. zviss. Mik., xviii, 1902, p. 305, and 

 xix, 1902, p. 68) confirmed later by Nocht, Reuter, and Giemsa, 

 this dye is Methylenazur, an oxidation-product of methylen blue, 

 already described by Bernthsex in 1885. It is an energetic dye, 

 of markedly metachromatic action, and to it are due the meta- 

 chromatic effects of methylen blue solutions (methylen blue itself 

 is not metachromatic). 



The presence of this dye as an impurity in methylen blue is not 

 always an undesirable factor ; on the contrary, it sometimes affords 

 differentiations of elements of tissues or of cells that cannot be produced 

 by any other means. Methylen blue that contains it is known as poly- 

 chrome methylen blue, and is employed for staining certain cell-granules. 

 Unna (Zeit. zviss. Mik., viii, 1892, p. 483) makes this as follows : A 

 solution of 1 part of methylen blue and 1 of carbonate of potash in 20 

 of alcohol. and 100 of water is evaporated down to 100 parts. (It may 

 be used at once, or after diluting with an equal volume of anilin water, 

 for sections, which after staining may be differentiated with glycol, 

 creosol, or Unna's glycerin-ether mixture — all of which, as well as the 

 polychrome methylen blue, can be obtained from Griibler. Micn.ELis 

 {op. cit.) makes it as follows : 2 gr. of medicinal methylen blue are 

 dissolved in 200 e.c. of water, and 10 c.c. of i\, normal solution of 



189 



