Nitro and Azo Dyes 



91 



still used, however, as a mucin stain, and is good for vital staining 

 and for staining in bulk. It is employed in staining cellulose walls 

 of plants in contrast to hematoxylin; and occasionally for staining 

 bacteria in contrast to gentian violet in the Gram technic, to 

 methyl or crystal violet in the Ljubinsky stain for diphtheria or- 

 ganisms, or to carbol-fuchsin for staining acid-fast bacteria. 

 Blaydes (1939) points out that it stains more intensely if used in 

 phenolic solution. 



r I I I I n 



H 



-J 

 o 



400 



I I I I I I I ^?^^^ I I I 

 460 520 580 640 

 WAVELENGTH iTI^Ji 



Fig. 10. Spectral curves of two azo dyes: 

 1. Bismarck brown Y. 2. Chlorazol black E. 



I J 

 700 



A caution to observe in connection with Bismarck brown is 

 that solutions should not be boiled before using, because the 

 composition of the dye is changed by heat. 



A spectrophotometric curve of this dye is given in graph 1, Fig. 

 10. 



For technic as mucin and cartilage stain in contrast to methyl green, see Staining 

 Procedures, p. IA4-5. 



For technic of Ljubinsky stain for diphtheria, see Id, IIIA2-I2. 



