Metachromatic interactions of toluidine blue with heteropolyanions

Abstract

Tungsto 12-zincic acid, potassium 13-vanadomanganate, potassium 13-vanado nickelate, potassium 11-tungsto phospho-nickelate, potassium 11-tungsto cobaltosilicate, ammonium 11-tungstodicobaltoate and sodium 12-tungsto borate have been shown to induce metachromatic effects in toluidine blue; the effects being hypochromacity coupled with hypsochromic shifts.The titration profiles of dye-heteropolyan- ion meta-chromatic complexes versus MgCl₂, KCl and HCI show three distinct portions indicating two other distinct types of interactions in addition to the electrostatic interaction between positively charged toluidine blue dye and negatively charged heteropolyanion surfaces.