Xitro and Azo Dyes 83 



This is another dye which is turned red by excess of alkah and 

 has therefore some use as an indicator. McLean and Ireland 

 (1940) have employed it with malachite green for staining sections 

 of roots or stems of plants. 



c76 ORANGE II C. I. NO. I51 



Synonyms: Gold orange. Orange A, P, or R. Acid orange II ^ 

 Y or A, Orange extra. Mandarin G. Tropaeolin 000 No. 2. 



N = N 



NaS03 

 Ci6HiiN204SNa; Mol. WL 350.321 



{An acid dye; absorption maximum about 4SS-487) 



Solubility at 26° C: in water 11.37%; in alcohol 0.15% 



This dye, which differs from orange I only in the position of the 

 hydroxyl group on the naphthalene radical, is similar to it in color 

 and properties, but does not change color with changing reaction 

 of its solution. This dye is rarely employed in microscopic work, 

 and yet may be recommended as a valuable substitute for orange 

 G when a stronger yellow is desired for contrast purposes. Thus 

 French (1926b) uses it in combination with eosin and azure C in a 

 general tissue stain. It has been used by Bergonzini (1891) in 

 place of orange G in the Ehrlich-Biondi stain; and by Ebbinghaus 

 (1902) for staining keratin in sections of skin. Kalter (1943) in- 

 cludes it in a quadruple staining method, the other dyes in com- 

 bination with it being fast green FCF, safranin O and crystal 

 violet. 



A spectral curve of this dye is given in graph 3, Fig. 7, p. 74. 



c78 NARCEIN C. I. NO. 151 



H OH 



I 



NaS03_/~^_N_N 



\_/ I 



NaSOg 



C,6Hi2N207S2Na2; Mol. Wt. 454.386 



{An acid dye) 



Solubility at 26°C: in water 10.02%; in alcohol 0.06%) 



This dye is a derivative of orange II, prepared from the latter 

 by treatment with sodium bisulfite. It is rarely used either as a 



