Define the Primary Stain and Mordant?
(i) Primary Stain - Crystal violet is the primary or first stain, which stains all the cells violet/purple.
(ii) Mordant - Gram's iodine serves as mordant. It binds with primary stain to form insoluble complex, crystal violet-iodine (CV-I) complex, that intensify the colour of the stain. At this point, all cells will appear purple - black.