MAKING COVER-GLASS PREPARATIONS 27 



If the mixture is not clear, add more of the saturated alco- 

 holic solution of fuchsin drop by drop until when viewed 

 through the pipette by transmitted light the liquid is perfectly 

 clear. 



ANILINE GENTIAN VIOLET (EHRLICH-WEIGERT) 



Saturated alcoholic solution of gentian violet 1 1 cc. 



Absolute alcohol . . 10 cc. 



Aniline water . 100 cc. 



It is more convenient for each student to prepare one fifth 

 of this quantity. 



CARBOLIC THIOXINE BLUE (NICOLLE) 



Thionine blue . . i gram 



CarboHc acid . . 2.5 grams 



Distilled water . 100 cc. 



Filter. Before using, dilute with an equal quantity of distilled 

 water and filter again. 



CARBOLIC GENTIAN VIOLET (NICOLl£) 



Gentian violet (saturated alcoholic solution) . 10 cc. 

 Carbolic acid (i % solution) . 100 cc. 



Mix and filter before storing. 



38. Aqueous solutions. Aqueous solutions of methyl violet, 

 gentian violet, fuchsin, and the other aniline dyes are prepared 

 by adding i cc. of the saturated alcoholic solution of the 

 desired dye to 20 cc. of distilled water. This will impart a 

 decided color to the liquid, so that in a pipette it will be barely 

 transparent. 



The true aqueous solutions are made by dissolving the dyes 

 in water, but these are weak and not so effective as those pre- 

 pared from the alcoholic solutions. These solutions deteriorate 

 in a short time. The carbol fuchsin and alkaline methylene 

 blue will keep a little longer, but they require filtering occa- 

 sionally. 



