BACTERIOLOGICAL TECHNIC 43 



be rejected. If the medium has shrunk from the effects of evapo- 

 ration it should be rejected, or the evaporated water may be re- 

 placed and the medium sterilized again. 



SECTION 6 



PREPARATION OF STAINING SOLUTIONS 



Saturated alcoholic solutions of stains are prepared 

 by covering the anihn dye with absolute or 96 per 

 cent alcohol and allowing it to stand with frequent 

 agitation until no more stain is dissolved. Other 

 solutions for the preparation of stains are: 



1. Solution of potassium hydrate in water i : 10,000. 



2. Solution of carbolic acid in water (5 per cent). 



3. Anihn water, prepared by shaking 2 c.c. anilin 

 oil with 100 c.c. water and filtering through filter 

 paper until clear. 



The following four stains are most commonly in 

 use for morphological studies of bacteria: 



1. Loffler's methylene blue — 



Saturated alcoholic solution of methylene blue 30 c.c. 



Potassium hydrate in distilled water i: 10,000 70 c.c. 



2. Ziehl-Neelsen's carbol-fuchsin — 



Saturated alcoholic solution of fuchsin 10 c.c. 



5 per cent solution carboUc acid in distilled water 90 c.c. 



3. Ehrlich's anilin gentian violet — 



Saturated alcoholic solution of gentian violet 25 c.c. 



Anilin water (2 per cent) 75 c.c. 



4. Gram's iodin solution — 



lodin I gra,m 



Potassium iodid 2 grams 



Dissolve in a few cubic centimeters of distilled 



