148 Biological Stains 



CTI3 





C21H22N3CI; Mol. Wt. 351.867 



{A basic dye; absorption maximum about 55 J/) 



n5 New Fuchsin (Magenta III) c. i. no. 678 



Synonyms: Isorubin. Fuchsin NB. 



This compound is tri-methyl fuchsin, or triamino-tritolyl- 

 methane chloride: 



CH3 



I 

 H CI /""\ NH. 



N_/~\_C 



_. „ ~\_NH2 



H I \^/ 



CH3 I 



CHa 



C22H24N3CI; Mol. Wt. 365.893 



{A basic dye; absorption maximum about 556) 



Solubility at 26° C: in water 1.13%; in alcohol 3.20% 



From the general rule concerning alkyl substitution it will be 

 understood that new fuchsin is the deepest in shade of these four 

 dyes, pararosanilin the least so. The commercial fuchsins, there- 

 fore, which consist of mixtures of the first three vary in depth ac- 

 cording to the proportions in which they are present. 



A typical spectrophotometric curve of rosanilin (Magenta I) 

 is given in Fig. 20. Those for Magentas O, II, and III are not 

 given here, as they are so nearly the same that they can be dis- 

 tinguished only by careful measurement, and the differences 

 would not show in such a graph as those here included. 



It has proved from the investigations of the Stain Commission 

 that not all basic fuchsins furnished as biological stains are mix- 

 tures of these three compounds. Many of the samples prove to be 

 fairly pure pararosanilin; while others are deeper in shade than 

 rosanilin and presumably contain appreciable quantities of 

 magenta II. All of these dyes differ so very slightly from each 



