methyl violet 2B together with an equal weight of dextrin. Yet in 

 actual test, none of these preparations proves any better than 

 crystal violet or methyl violet 2B, unless it be possibly in inhibit- 

 ing the growth of Gram-positive bacteria. Unfavorable reports 

 of crystal violet for this purpose have been received; but tests 

 of several samples of crystal violet now on the market show 

 them to be bacteriostatic to a higher degree than the sample of 

 pre-war gentian violet with which they were compared. 



Under the circumstances the Commission has faced a difficult 

 problem in trying to standardize gentian violet. The question has 

 been whether to recognize the name at all, or to approve some par- 

 ticular dye or mixture of dyes of this group as gentian violet. The 

 former course was almost impossible because of the wide demand 

 among biologists for gentian violet under that name. The second 

 course (unless considerable latitude be recognized) would be en- 

 tirely arbitrary, inasmuch as no information is available to show 

 which members of this group of dyes are especially needed in hist- 

 ology or bacteriology. Accordingly the Commission has finally 

 defined gentian violet as either penta-methyl or hexa-methyl para- 

 rosanilin, or else a mixture of methylated pararosanilins composed 

 primarily of the two compounds just named and having a shade at 

 least as deep as that recognized in the trade as methyl violet 2B. 

 Gentian violet, must, moreover, prove satisfactory in actual use 

 as determined by the tests proposed by the Commission (see 

 specifications page 135). This definition will not exclude anything 

 now sold as gentian violet except those that do not prove satis- 

 factory in performance. At the same time the Commission does 

 not wish to give official standing to gentian violet and recommends 

 that crystal violet be ordinarily ordered in its place. 



METHYL GREEN C. I. NO. 684 



Synonyms: Double green. Light green. 

 {A basic dye; absorption maximum about 633.8) 



Methyl green is crystal violet into which a seventh methyl group 

 has been introduced by the action of methyl chloride or methyl 

 iodide upon it, forming the compound:* 



*This ordinarily occurs in trade as a zinc double salt. 



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