PRACTICAL BACTERIOLOGY. 



rubber cap. Decomposition takes place much more 

 quickly if it is left in the light. If it is desirable to 

 still further increase its staining power, a solution of 

 caustic soda (1 : 1000) may be added to it drop by 

 drop, until the originally clear red fluid begins to 

 become turbid; after this no more should be added, or 

 precipitates will be formed. In this so-called " critical 

 condition " the solution cannot be kept for nearly so 

 long a time as before. 



This staining solution is the most powerful which 

 is at present known. Ehrlich's solution, which is 

 nearly as powerful, is prepared as follows : — 100 ccm. 

 of aniline water, prepared as described above, is 

 mixed with 11 ccm. of concentrated alcoholic solu- 

 tion of fuchsine. This preparation can only be kept 

 for at most two or three weeks. Gentian violet or 

 methyl violet may be used instead of fuchsine for 

 either solution ; methylene blue is less suitable. 



Ziehl's carbolic fuchsine is a staining fluid which 

 may be kept for any length of time, and which is very 

 nearly as efiectual as the ones prepared with aniline 

 water. The simplest mode of preparing it is to mix 

 100 ccm. of water with 5 grm. of carbolic acid and 1 

 grm. of fuchsine. Frequently 10 ccm. of alcohol are 

 added as well, but this is not necessary ; it is true 

 that the fuchsine is more easily dissolved by its 

 means, but, on the other hand, the staining power of 

 the solution is diminished. Instead of the fuchsine. 



