their chromophore. For this reason one of the quinoid formulae 

 seems preferable; and for the sake of uniformity the paraquinoid 

 form will be given in the following pages. It must be remembered, 

 however, that the other formulae are equally admissable; and it is 

 possible that the compound occurs in two or even all three of the 

 different forms. 



PYROXIN G 



c. I. NO. 739 



CH, 



CH, 



\ 



I 



/ 



N 



CH3 



/ 

 _X— CH3 



"I 

 CI 



{A basic dye; absorption maximum about 5^5.) 



This dye finds its principal use as a stain in the Pappenheim 

 combination, where it is employed with methyl green for staining 

 basophile elements, especialty the mast cells, and for staining the 

 gonococcus in smears of pus. It is also used sometimes as a counter 

 stain in the Gram technic for bacteria; and by Ehrlich as a com- 

 ponent of certain "neutral" stains. Since the war it has proved 

 difficult to obtain this dye in America except by importation, as 

 the intermediate from which it is manufactured is very difficult to 

 prepare and is not produced in this country.* 



CH.CH 



3 ^^^2 



\ 



N 



PYRONIX B C. I. NO. 741 



CH.CH3 

 O /\_N— CH. •CH3 



CH.CH 



3 '-'^^2 



{A basic dye; absorption maximum about 550.) 



This dye differs from pyronin G only in that it is an ethyl in- 

 stead of a methyl derivative. As a result it is very slightly deeper 

 in shade but has almost identically the same staining behavior. 

 Investigations recently carried on by the Commission indicate that 

 it can replace pyronin G in the Pappenheim stain and probably in 

 all its other uses. This is very encouraging, for it is much more 

 easily prepared and a very satisfactory product of American 

 manufacture is now available. 



*For literature references to the procedures mentioned in this chapter see 

 pp 110 to 128 and 138 to 145. 



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