[Histonet] amphoteric dyes

[Jennifer MacDonald]

Can anyone help clarify amphoteric dyes for me?  I have read conflicting information.  A couple of sources state that amphoteric dyes are cationic if the pH is below the IEP and anionic if the pH is above the IEP.  Other sources state the opposite.
 
Also, what is the purpose of the potassium metabisulfite after the gold chloride toning step in the Gomori Reticulin?
 
Jennifer MacDonald