Enzymes 



171 



are surrounded by a colored halo. To circumvent this diffi- 

 culty, Seligman and associates^ have suggested the use of 

 esters of highly insoluble naphthols (such as 6-bromo-^- 

 naphthol), in the absence of a diazonium salt, whenever in- 

 cubation must be carried out at a low pH. The precipitated 

 naphthol could then be azo-coupled in a second step, at an 

 alkaline reaction. The idea sounds feasible but does not work 

 well in practice. Naphthols insoluble enough to precipitate 

 with a sharp localization will not couple unless enough or- 

 ganic solvent ( acetone, alcohol ) or strong alkali is added to 

 effect some degree of solution. However, under such con- 

 ditions, gross blurring of the picture will result. For this rea- 



TABLE 1 



Composition and Trade-Name 

 of Compound* 



Tetrazotized o-dianisidine (Diazo Blue B 

 Salt) 



Diazotized naphthylamine 



Diazotized 4-cliloro-2-aminoanisole (Diazo 



Red RCSalt) • ••• 



Diazotized 3-nitro-4-aminoanisole (Diazo 



Bordeaux GP Salt) • ■ 



Diazotized 5-nitro-2-aminoanisole (Diazo 



Red B Salt) ,•• 



Diazotized 3-nitro-4-aininoanisole (Diazo 



Red G Salt) • ■• 



Diazotized 4-nitro-2-aminoanisole (Diazo 



Scarlet R Salt) ••• 



Diazotized ortho-amino-azotoluene (Diazo 



Garnet GBC Salt) .-..•• 



Diazotized 4-benzoylamino-2,5-dimethoxy- 

 aniline (Diazo Fast Blue RR Salt) 



To Be 



Used with 

 Naphthol 



a 



AS 

 a 



AS 



a 



a 



a 



a 



Shade of 

 Azo Dye 



Purple-black 

 Purple 

 Deep blue 



Black 



Carmine red 

 Carmine red 



Red-brown 



Purple-brown 



Red-brown 



Red-brown 



Red-brown 

 Red 

 Carmine red 



Black 



Purplish red 

 Purplish blue 



* The proprietary names of these compounds may vary slightly with individual 

 manufacturers. However, if ordered by the trade-names listed above, they will be 

 readily identified. 



2. Seligman, A. M., Nachlas, M. M., Manheimer, L. H., Friedman, O. M., 

 and Wolf, G.: Ann. Surg., 130:333, 1949. 



