NILE BLUE SULFATE C. I. NO. 913 



Synonym: Nile blue A. 



{A basic dye; absorption maxima about 64-^.5, [592.2] ) 



The use for which this dye is best kno^^'n to the biologist is the 

 Lorrain Smith fat stain. In this procedure the dye is boiled with 

 dilute sulfuric acid, and thus hydrolyzed, with the introduction of 

 oxygen in the place of the radical XHo (S04)k> in other words pro- 

 ducing a new dye of the class known as oxazones. This oxazone 

 dye is red, and is fat-soluble. Nile blue sulfate itself, on the other 

 hand, is not fat-soluble but combines readily with fatty acids. As 

 a result the technic serves to distinguish between the free fatty 

 acids in histological material and the neutralized fats, the former 

 staining blue, the latter red. 



Nile blue sulfate is also used unaltered for staining living tad- 

 poles previous to making transplants, in order to distinguish the 

 grafts. 



CRESYL VIOLET 



Synonym: Cresylecht violet (i.e., cresyl fast violet). 

 {A basic dye; absorption maximum about 585.) 



No information is at hand concerning the exact chemical form- 

 ula of this dye. It is understood to be a derivative of brilliant 

 cresvl blue. 



Cresyl violet is not a widely used stain, but finds some employ- 

 ment on account of its strongly metachromatic properties. It is 

 valuable in making permanent preparations of nervous tissue. 

 According to Ehrlich (1910, II, p. 78) it stains nuclei violet, plasma 

 blue, amyloid, mucin and mast cell granules red. Williams (19*23) 

 uses it for staining sections of fresh tumor tissue. 



As cresyl violet is not a textile dye, some difficulty has been 

 found in obtaining it for biological purposes. Williams reports con- 

 siderable trouble in this respect. Spectrophotometric examination 

 of the pre-war material used by Williams shows it to have been a 

 mixture, apparently of cresyl violet with another dye of more red- 

 dish cast. (See Ambler and Holmes 1924.) The domestic sample 

 with which he obtained unsatisfactory results on account of its 

 entire lack of metachromatic properties was this unknown red dye 

 alone; while the domestic sample with which he obtained good 

 results, altho not identical with those obtained with the pre-war 



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