Nitro and Azo Dyes 71 



This dye is rarely used as a biological stain, but is called for by 

 Schaffer for staining sections of bone, and by Unna in certain stain 

 mixtures used in studying the phenomenon called by him chro- 

 molysis. Fast yellow G or GG is employed by Wallart and Hou- 

 ette (1934), together with hennatoxylin and acid fuchsin, in a 

 trichrome staining technic. 



c5 OIL YELLOW II C. I. NO. 1 9 



Synonyms : Butter yellow. Oil yellow D. Fast oil yellow B. 



C14H15N3; MoL Wt. 225.284 



Butter yellow is the most common designation for this dye in the 

 biological literature. The name is unsatisfactory for two reasons; 

 first, it sometimes falsely suggests some relationship to butter; 

 second, it is ambiguous because C. I. No. 17 (amino-azo-toluene) 

 is also called butter yellow. For these reasons the name given in 

 the above heading is preferred; or one may definitely specify it 

 by the chemical term, p-dimethyl-amino-azo-benzene. 



It has not been used, apparently, as a stain, but has been con- 

 siderably studied as a carcinogenic substance, so much so that 

 fear has been expressed in some quarters that the public might 

 come to associate cancer with butter and that this food might be 

 thereby discredited. 



c8 CHRYSOIDIN Y C. I. NO. lO 



Synonyms: Brown salt R. Dark brown salt R. 



N__N 



C12H13N4CI; Mol. Wt. 248.713 



{A basic dye; absorption maximum about ^61) 



Solubility at 26°C: in water 0.86%; in alcohol 2.21% 



This dye is a good substitute, in some procedures, for Bismarck 

 brown. Like the latter, it is easily injured by heat, and boiling 

 should be avoided in preparing solutions. Maheshwari and Wulff 



(1937) have employed it in the vital staining of pollen tubes; Lison 



(1938) for the vital staining of insects. Monn^ (1939) uses it to 

 demonstrate the Golgi apparatus. Varco and Visscher (1941) in- 

 clude it among a series of dyes employed in the study of gastric 

 secretion. 



