90 Biological Stains 



Little attention was paid to the suggestion, however, until quite 

 recently when the paper was discovered almost simultaneously by 

 Ruth (1946) and Leach (1946) both of whom found the Curtis 

 modification a useful one as it is less subject to fading. 



D18 ORSEILLIN BB C. I. NO. 184 



CHj 



1 / 



NaSO, 



SOjNa 

 C24Hi8N407S2Na2; MoL Wt. 584.530 

 {An acid dye; absorption maximum 523) 



Cohen and Doak (1935) employed this dye in contrast to crystal 

 violet for staining a mycorrhizal fungus on the roots of plants. 

 Subsequently other authors including Alcorn and Yeager (1937), 

 Keener (1951), have used it for staining other fungal parasites. 

 Maneval (1941) lists it among several useful bacterial stains. 



d21 BISMARCK BROWN Y C. I. NO. 33 1 



Synonyms: Vesuvin. Phenylene brown. Manchester brown. 

 Excelsior brown. Leather brown. Basic brown G, GX, or GXP. 



Slightly different shade: Bismarck brown G. 



(A basic dye; absorption maximum 463. Solubility at 26° C: 

 in water 1.36%; in alcohol 1.08%) 



The various shades of Bismarck brown are mixtures of different 

 compounds, the most important of which are salts of the following: 



N = N 



/ \ NH2 



/\ / \ 



NH2 



N = N 



\ NH2 



/ \ 

 \ / 

 NH2 



The dihydrochloride is CisHzoNgCla; MoL Wt. 419.318 



This dye was formerly employed quite extensively as a contrast 

 stain, but has now been replaced to some extent by others. It is 



