SECTION ONE 



The fuchsinic acid dyes are exceptional in that their molecules 

 contain multiple dye-ions of different kinds. In the solid state 

 these unions of different dye-ions are stable, but in solution a 

 degree of ionization takes place with competition between the 

 different kinds of dye-ions for different kinds of tissue-elements. 



In the case of the more complex fuchsinic acids in solution, 

 even in the absence of tissue elements or other stainable material, 

 competition exists between the different component dye-ions of 

 the same molecule. An example of this is to be found in tri- 

 favioxanthic acid where the solution changes colour due to con- 

 flict between the different component dye-ions signifying a change 

 in the structure of the molecule. 



Work on pH measurements of all dyes used in biology is now 

 proceeding in the author's laboratories and the results will be 

 published when the task has been completed. Meanwhile, it is 

 thought that the above Tables, although incomplete, may be of 

 interest to medical and biological research workers. 



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