Studies in Adsorption

Abstract

Relative rates of adsorption by gelatin and by wool have been determined for a number of series of sulfonated azo acid dyes and 2: 1 dye-metal complexes. It is shown that: (i) The rate of adsorption of each dye by a given area of the external surface of gelatin is about four times that by the same area of the external surface of wool; (ii) the logarithm of the rates falls linearly with both the number of substituent groups in the dye molecule and with its molecular volume; each series of dyes gives points lying on a different line. A few experiments, including measurements of absorption spectra, are described in which benzyl alcuhol and other organic solutes have been added to the dyebath. Benzyl alcohol, and to a less extent dioxan, tends to disaggregate dyes of low basicity when added to their aqueous solutions, but D-glucose and inositol do not do so. Of these solutes, only benzyl alcohol is effective in accelerating dyeing. It is considered that the mecha nisms already proposed to account for the acceleration of dyeing by addition of solvents probably all operate, but the most important may be the effect of adsorption of the solvent by the fiber. On the basis of the present results, the very rapid adsorption of benzyl alcohol by wool is attrihutahle to its low molecular volume and nonionic nature.