zene ring is attached to it. This pentavalent nitrogen allows the 

 compounds to behave like ammonium bases; so with the amino 

 groups which are always present, the basic properties of these dyes 

 are very strong. The theoretical base of the simplest safranin 

 would have the formula : 



N=/\. 



H.N / \ NH, 



OH 



This form of ammonium base does not actually exist, as the safranin 

 bases really occur in the form of anhydrides; but salts of these 

 ammonium bases are the commonly known dyes. The commercial 

 dyes are ordinarily chlorides. 



There are two groups of safranins : the benzo-saf ranins in which 

 the azin group unites two benzene rings; and the naphtho-saf ranins 

 in which it unites two naphthalene groups. The simplest safranin 

 is pheno-safranin, which is the chloride of the theoretical base just 

 given, namely: 



N_ 



H,N / \ NH 



The commercial safranins are ordinarily methyl or ethyl substitu- 

 tion products of this; or occasionally phenyl substitution products. 

 The one of greatest value to the biologist is generally called Safra- 

 nin O. 



SAFRANIN O C. I. NO. 84 1 



Slightly different shades: Safranin AG, T, MP, Y, and G. (Altho 

 all included in C. I. No. 841 they are different from the grade 

 here described.) 



(A basic dye; absorption maximum about 515.) 



The common safranins of commerce, under various shade 

 designations, are mixtures of di-methyl and tri-methyl pheno- 

 safranin : 



CH3 



"N=\/\ 

 H,N / \ NH3 H^ / \ NHa 



/\ CI 



55 



