The chemical forms of pH and metalloehromic indicators adsorbed onto porous Vycor glass are determined by visible absorption spectroscopy. Methyl Red is adsorbed on porous Vycor glass in a red protonated form. A proton is donated from the active silanol residue on the surface of porous glass to the nitrogen atom of Methyl Red, leading to formation of a hydrogen bonding. Xylenol Orange is adsorbed on porous glass from an aqueous solution in a manner similar to the coordination to a metal ion as a metalloehromic indicator. On adsorption, the proton of the phenol residue of the Xylenol Orange is dissociated and the imino and carboxyl groups play a role in adsorption as binding sites to the silanol group of porous glass. The adsorbed Xylenol Orange is exchanged by EDTA, dissolving into solution. It also reacts with copper(II) ion, forming a complex soluble in water.
ASJC Scopus subject areas
- Chemical Engineering(all)