STAINING, PRACTICAL AND THEORETICAL 



XANTHENE GROUP 



This group of dyes contains a number of sub-groups. One of 

 the most important of these, as far as the biologist is concerned, 

 is the fluorene group, perhaps better known as the amino deriva- 

 tives. Among the amino derivatives are : 



(a) The pyronines, examples of which are pyronin B and 

 pyronin Y (or G). 



(b) The rhodamines, which include rhodamine B and rhod- 

 amine 6G. 



The hydroxy derivatives (fluorone dyes) is another division. 

 Among these are the fluoresceins, eosins, phloxines, rose Bengal, 

 and gallein. 



The xanthene group also includes the anthrahydroxyphthaleins, 

 which constitute a very small subdivision, consisting of only four 

 or five members, only one of which (coeruleine) is used in micro- 

 technique. 



Aminoxanthene dyes contain the following resonance hybrid as 

 their chromophore : 



<R 



where R = hydrogen or a benzene or a naphthalene nucleus. 

 The hydroxyxanthenes are stabilized, by the loss of a proton, to 

 form an uncharged system having the quinoid structure, as follows, 

 as the chromophore : 



