MEDICAL AND BIOLOGICAL STAINING TECHNIQUES 



SPECIFIC GRAVITIES (at 4° C.) 



STAIN SOLUBILITIES AND MOLECULAR WEIGHTS 



Notes: 



The letters A, B and N indicate acid, basic and neutral dyes. 



Many stains in aqueous solutions, particularly dilute aqueous solu- 

 tions, are attacked and decomposed by airborne micro-organisms when 

 kept in stock for any length of time, e.g. eosin, aniline blue. In such 

 cases it is best to add a small crystal of thymol or a few drops of chloro- 

 form as preservative. In the case of alcoholic solutions such precautions 

 are unnecessary, since the alcohol itself acts as a preservative, preventing 

 the growth of such airborne micro-organisms. 



Solutions of auramine decompose when heated above 35-40° C. 

 Aqueous solutions of eosin should be prepared by using water of a 

 slightly alkaline reaction as traces of acid cause precipitation of the acid 

 radicle of the dye and consequent loss of staining affinity and colour. 

 Water buffered pH 7-2-8-0 gives good results with eosin. Alkaline 

 solutions of methylene blue decompose when heated above 60-65° C. 



Approximate 



percentage solubilities 



at 15° C. 



In water In alcohol 

 20-0 

 40-00 

 i-oo 



A 

 A 

 A 

 A 

 B 



Stain 

 Acid green . . 

 Acetyl yellow 

 Acid brown, R 

 Acid yellow, S 

 Acridine orange 



Mol Wt. 



792-83 

 401-22 

 400-00 

 380-24 

 556-02 



2-00 

 0-50 



4-0 



o-oi 

 o-oi 

 nil 

 0-50 



430 



