160 Biological Stains 



N30 CRYSTAL VIOLET C. I. NO. 68 1 



Synonyms: Violet C, G, or 7B. Hexamethyl violet. Methyl violet 



lOB. Gentian violet. 



C25H30N3CI; Mol. Wt. 407.971 



{A basic dye: absorption maximum 589-593) 



Solubility at 26°C: in water 1.68%; in alcohol 13.87% 



This dye is a hexa-methyl-pararosanilin, whose formula is given 

 above as one of the components of methyl violet. The Commis- 

 sion has made as careful an investigation of this dye as of any other 

 and recommends it highly. 



Methyl or gentian violet is of chief value to the biologist as a 

 nuclear or chromatin stain, having many histological and cyto- 

 logical applications, the one for which it is most commonly used at 

 present being the Flemming (1891) triple stain in which it is em- 

 ployed with orange G and safranin — a technic which gives a very 

 high degree of cytological differentiation. It is also used for 

 staining amyloid in frozen sections of fresh and fixed tissue, and 

 for staining the platelets in blood while it is much used by the 

 Weigert (1887) technic for staining fibrin and neuroglia. The 

 bacteriologist also finds it a useful stain and probably purchases 

 more at the present time than all other biologists together; the 

 chief bacteriological use is in the Gram technic for distinguishing 

 between different kinds of bacteria. A further more recent use is 

 in bacteriological media for inhibiting the growth of Gram-positive 

 organisms, due to its selective bacteriostatic action. An important 

 example is Petroff's (1915) gentian violet egg medium for isolation 

 and cultivation of the tubercle organism. For most of these pur- 

 poses, crystal violet is in general use. As a result of its bacterio- 

 static properties it has come into use as a medicinal agent for the 

 control of staphylococcic infection. It has not yet been definitely 

 established, however, whether crystal violet a.lone or some mixture 

 thereof with the lower homologs should be used for this purpose. 



The Flemming and Gram stains have seemed the most delicate 

 procedures for which it is used; so they have been given the most 

 careful study. In the case of the Gram stain it was discovered that 

 there are a score or more different procedures all referred to by the 

 name "Gram** stain, and a study was made of all the methods that 

 were found (see Hucker and Conn, 1923). The result of the in- 

 vestigation was to conclude without reservation that crystal violet 

 may be substituted for gentian violet in both the Gram and Flem- 

 ming technics, and probably for gentian or methyl violet in any of 

 the bacteriological or histological methods for which either stain 

 is designated. The advantage of crystal violet is obvious; for it 

 is a definite chemical compound, while methyl and gentian violet 

 are both variable mixtures. 



It is of interest to note that in the literature of microscopic tech- 



