STAINING, PRACTICAL AND THEORETICAL 



As already indicated, the chemical hypothesis was verified by 

 the synthesis and isolation of each of these compounds in the 

 pure form. The syntheses were confirmed by chromatography and 

 electrophoresis. Although these and other fuchsinic acid com- 

 pound dyes are now available commercially it appears that the two- 

 stage techniques (e.g. Falg, page 198) are to be preferred to the 

 one-step methods (e.g. Trifalgic acid, page 200) in histology 

 and cytology. However, one of the compound dyes (trifalgic 

 acid) has been found to be of value in protein-electrophoresis by 

 Dr. John Bodman (Bodman, i960), who kindly tested a sample 

 of the dye for us electrophoretically. Among other compound 

 fuchsinic acid dyes later discovered were the Faviolic acids. 

 These are formed in the same manner as are the Falgic acids, 

 the difference being that violamine 3B was used in place of light 

 green. 



The name of this series was derived from Fa for acid fuchsin 

 and Violic for violamine 3B. Using the symbol Fa again to 

 denote the acid fuchsin radical, and V to denote the violamine 

 radical we have : 



1. FaV = monofaviolic acid (red). 



2. FaV2 = difaviolic acid (violet). 



3. FaVs = trifaviolic acid (blue). 



Another series is the FADIANIC acids produced by the inter- 

 action of acid fuchsin and dianil blue 2R. Many other compound 

 fuchsinic acids have since also been isolated. Some of these will be 

 dealt with elsewhere in literature. Only the compounds of acid 

 fuchsin-light green (Falg technique and modifications) acid 

 fuchsin-violamine (basic Faviol technique) and acid fuchsin-sun 

 yellow-violamine (standard Faviol technique), will be discussed 

 here, in brief. 



THE FALG TECHNIQUE 



Practical details for carrying out this procedure are given on 

 page 198. It should be noted that the light green attaches itself 

 to those tissue elements that have already been stained by the acid 

 fuchsin ; and indeed to the stain (acid fuchsin) by which they have 

 been stained. This is a special kind of counterstaining. We have 

 to distinguish here between two chief kinds of staining, primary 



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