Abstract
SummaryInorganic anions retard the dyeing of anionic dyes on anodic alumina films. The effect becomes more marked with increase in the valency of the inorganic or the dye anion, and it is attributed to repulsion between the inorganic and the dye anions at the surface and competition between them for ionic sites. Sulphate, such as sodium sulphate, is very effective in preventing dyeing of dyes with at least two sulphonate groups in the molecule, and phosphate is even more effective. The results support the hypothesis that the dyeing process is adsorption partly by ion exchange and partly by covalent bonding with aluminium atoms in the surface. The dye anions appear to be more readily exchangeable with sulphate ions when ion exchange adsorption takes place than when they are adsorbed by covalent bonds. Experiments with alizarin and its sulphonate show that mordant dyes are probably adsorbed as negatively charged ionic micelles of the dye-metal chelate complex. It is suggested that this is the mechanism by w...
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