ZIEHLS CARBOL-FUCHSINE 83 



The solution prepared as above should not be kept for 

 longer than about two weeks, but should be made fresh and 

 filtered before use. 



Ziehl's Carbol-Fuchsine. — This stain is much the same as 

 the above, except that, instead of aniline, carbolic acid 

 (phenol) is used as the mordanting agent. The solution 

 is prepared by taking : 



Fuchsine ... ... ... ... 1 gramme 



Phenol ... ... ... ... 5 grammes 



Distilled water ... ... ... 100 c.c. 



The fuchsine is very finely powdered and added to the 

 water, together with the phenol ; the whole is allowed to 

 stand, with frequent agitation, until dissolved. Frequently 

 10 c.c. of alcohol are added to dissolve the fuchsine more 

 easily ; but this is not necessary, and the addition reduces 

 the staining power of the solution. The solution is filtered 

 before use. This solution has the advantage over those 

 prepared with aniline, that it will keep any length of time, 

 although its staining power is not so great. 



Ldffler's Methylene Blue. — This solution is prepared by 

 taking : 



Saturated alcoholic solution of methylene blue 30 c.c. 

 Caustic potash solution (1-10,000) 100 c.c. 



This solution keeps well, and is very useful for those 

 organisms which are very apt to overstain with the two 

 preceding staining solutions, such as the Bacillus diphtheria, 

 sarcina, yeasts, etc. 



All the above staining reagents should be preserved in 

 the dark when not in use. 



Decolourising Agents. — It is found that when bacteria are 

 stained by any of the above methods, they can be made to 

 give up their stain, partly or wholly, by the application of 



6—2 



