Quinone-imine Dyes 135 



L50 NIGROSIN, WATER SOLUBLE C. I. NO. 865 



Synonyms: Nigrosin W, WL, etc. Gray R, B, BB. Silver gray. 



Steel gray. Indulin black. 



Nigrosin is not a pure dye, but is a mixture; and apparently the 

 composition of different lots may vary. Ordinarily it is a mixture 

 of a blue-black or violet indulin with a yellow dye in such a pro- 

 portion that the resulting blend appears black. As the proportion 

 of these two dyes is not always the same, different samples of 

 nigrosin may vary in the amount of blue apparent to the eye. 

 It is assumed that the biologist wants a nigrosin which appears 

 distinctly black; this is certainly true in those procedures where it 

 is used for a background stain. Accordingly the samples of 

 nigrosin submitted which have a bluish hue have been refused 

 certification by the Stain Commission. 



N'igrosin is used in place of India ink as a background stain in 

 the study of unstained bacteria ; also as a stain for the background 

 in contrast to fuchsin in the Dorner (1926) stain for bacterial 

 spores. It is recommended by Ehrlich for staining the tissue 

 of the central nervous system either alone or in combination 

 with other stains, and by Jarotsky for staining pancreatic 

 tissue following hematoxylin. Botanists use it in studying algae 

 and fungi. Pfitzer's (1883) picronigrosin serves as a chromatin 

 stain. Nigrosin is also used by Unna (1921) in combination with 

 **orange" (orange G.^) in the study of the process of chromolysis. 

 Bean (1927) has employed it as a counterstain for nervous tissue. 



For the use in negative staining of bacteria, see Staining Procedures, p. Ill A2-6, 

 For technic of Dorner spore stain for bacteria, see Id. p. IIIA2-9. 



