Phenyl Methane Dyes 143 



Brilliant green is used to some extent as a stain for bacteria, 

 spirochaetes, molds, and yeasts (see, for instance, Krajian, 1941), 

 but finds more frequent employment as a constituent of bacterio- 

 logical media. It is used, for example, as follows; (1) as a con- 

 stituent of Krumwiede's brilliant green bile media for plating 

 water in order to distinguish the colon organism from other lactose 

 fermenting organisms; (2) it is employed in media used in search- 

 ing for the typhoid organism in stools, where its value comes from 

 its ability to inhibit the colon organism; (3) it is used as a con- 

 stituent of enrichment media for the stimulation of the typhoid 

 organism, in which it must prevent the growth of the normal colon 

 types but not be toxic to the typhoid organism. It has proved 

 much more simple to find a brilliant green satisfactory for colon 

 diagnosis in water work than for the isolation and enrichment of 

 the typhoid organism. A paper by Rakieten and Rettger (1927) 

 has shown the difficulty encountered in this latter instance. 



As the first of three purposes above mentioned is the one for 

 which brilliant green is now most commonly used in America, all 

 samples submitted for certification are tested for use in the bril- 

 liant green bile medium. 



Spectrophotometric curves of typical samples of malachite 

 green and brilliant green are given in Fig. 18. All green dyes have 

 two absorption maxima, one about 430, the other about 620-630. 

 The primary maximum for malachite green, however,, is at a defi- 

 nitely shorter wavelength than that of brilliant green or either of 

 the two following dyes. 



m60 light green SF YELLOWISH C. I. NO. 67O 



Synonyms : -Light green 2G, S or 2GN. Acid green (with various 

 shade designations). Fast acid green N. 



This is a derivative of brilliant green, which is sulfonated and is 

 therefore an acid dye. 



NaS03_ 



C37H34N209S3Na2 ^Afoi. Wt. 792.832 



(Absorption maximum: 629-634, [428]) 



SdvinlUy at 26^0: in water 20.35%; in alcohol 0.82% 



Light green is a valuable plasma stain often used for staining 

 animal tissues in contrast to iron hematoxylin or other nuclear 

 dyes, although it fades badly if exposed to bright light. It is a 



