SECTION ONE 



Dye 



Molecular Michrome 



pH weight Group No. 



* The molecule consists of two dye-ions in association with a univalent 

 cation. 



t The molecule consists of two dye-ions in association with one univalent 

 anion. 



X The molecule has three dye-ions. 



§ Approx. 



^ This is not a dye but a colourless phenol used for producing colour in 

 certain plant tissues, as a test for lignin. 



An analysis of the above tables might bring some interesting 

 points to light. Thus, in the following Tables (pages 25-26) 

 which have been extracted from Table I, it will be seen that: 



(i) There is very little difference in the pH ranges between 

 acid and basic azine dyes commonly used in histology, 



(2) Of the acid oxazine dyes in common use, two are slightly 

 acid d ; one is neutral, and the others show pH values which are 

 very acid; two of the basic dyes are very acid in solution, as is 

 the amphoteric member of this group. 



(3) Four of the basic thiazine dyes are very acid in solution, 

 while one is quite alkaline. The latter dye (methylene violet, 

 Bernthsen) is an oxidation product of methylene blue. Gurr 

 (i960) quotes French (1926) as stating that in using Holmes and 



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