Phenyl Methane Dyes 155 



temperature (85°C.), fuming sulfuric acid containing sufficient 

 free SO3 to insure complete sulfonation to the trisulfonic acid, and 

 careful acidification to yield only the disodium salt. Since the 

 method which they proposed in this article was called to the atten- 

 tion of manufacturers, the American product has improved; it not 

 only gives permanent Van Gieson preparations, but proves more 

 satisfactory in the Mallory connective tissue stain. 



The spectrophotometric curve of a typical acid magenta I 

 (rosanilin) is given in Fig. 20 (curve 2), p. 149. The chief dif- 

 ference between this and the corresponding basic fuchsin is that it 

 has a distinct secondary maximum at about 500, where the curve 

 for basic rosanilin shows merely an almost imperceptible bulge. 

 A dye having its primary maximum at 500 would be orange in 

 shade, which is approximately the color of the acid phase of the 

 Andrade indicator. 



PROCEDURES RECOMMENDED BY THE COMMISSION IN WHICH THIS STAIN IS USED 



n20 HOFMANN S violet C. I. NO. 679 



Synonyms : Dahlia. Iodine violet. Red violet. Violet R, RR or 



4RN. Primula R water soluble. 



These various names are applied in a somewhat indiscriminate 

 way to dyes intermediate in shade between basic fuchsin and 

 methyl violet. Theoretically they are mixtures of methylated 

 and ethylated pararosanilins and rosanilins, having fewer than 

 five ethyl or methyl groups. Of these compounds, the formula 

 for tri-ethyl rosanilin is: 



CI 



I 



1 ^ 

 H 



H 



C26H32N3CI; Mol. Wt. 421.997 

 {A basic dye ) 



