530 H. J. CONN 



methyl and hexamethjd pararosanilins. The mixtures of 

 lower methylation have the most reddish cast of all the dyes in 

 the series and are generally designated as methyl violet. As 

 the mixture contains larger and larger amounts of more highly 

 methylated compounds, it becomes bluer in color and the suc- 

 cessive deeper shades are known in the textile trade as methyl 

 violet B, methyl violet 2B, methyl violet 3B, etc. Those com- 

 pounds designated as methyl violet 5B, 6B, and 7B, respectively, 

 are still bluer in shade and apparently contain a pararosanilin 

 in which a benzyl group has been introduced into one of the 

 amino-groups. 



The only textile dye in this series which if pure has a definite 

 chemical formula is crystal violet, which is hexamethyl pararos- 

 anilin. This dj'^e is quite a deep blue violet. 



In the earUer work already reported a comparison w^as made 

 of various commercial samples of methyl violet, methyl violet B, 

 methyl violet 2B, methyl violet 6B and crystal violet, which were 

 compared with certain samples obtained from difTerent biolog- 

 ical supply houses labeled as gentian violet. It was found that 

 crystal violet and methyl violet 6B were at least fair substitutes 

 for gentian violet in the Gram stain but that the methj'l violets 

 of lower methylation were unsatisfactory for this purpose. The 

 present investigation was planned as a more intensive study of 

 crystal violet and methyl violet 6B in comparison with gentian 

 violet. 



In the second series of tests there were included 10 samples of 

 crystal violet, 8 samples of methyl violet 6B, and 10 samples of 

 gentian violet. Of these 28 samples, 19 had been included in 

 the earher work. 



Two of the samples of crystal violet included in the earUer 

 work, namely those from the Providence Chemical Company, 

 and from Dicks David and Company, unfortunately had to be 

 omitted from the second test, due to the exhaustion of the samples 

 that had been investigated; but on the other hand in the present 

 work three samples of crystal violet, four of methyl violet 6B, 

 and two of gentian violet were added which w-ere not included 

 in the first tests. Of these 9 additional samples, three ■were 



