Left hand holds a ball an Anion. un ... an anionic dye in acid pH will tend to "switch off" its charge. If in the presence of a ionic group in the process of being "switched on" it will tend to form a saltlink. In the case of direct (anionic) dyes, the molecules are so large that saltlinkage is relatively unimportant, fixation taking place between pH 47. To DYEING Index (Top of Page ...