Effect of cation size on the enthalpy of dilution of alkali-metal salts of carboxymethylcellulose

Abstract

The intermediate and integral enthalpies of dilution of aqueous solutions of lithium, sodium, potassium, ammonium and caesium salts of carboxymethylcellulose have been measured at 25 °C. Constant values for the intermediate enthalpies of dilution are obtained with the lithium and sodium salts within the concentration range investigated, but the potassium, ammonium and caseium salts give progressively more exothermic values as the initial concentration is reduced. The integral enthalpies of dilution are in the order Li⁺ > Na⁺ K⁺= NH⁺₄= Cs⁺. Comparison with the corresponding series of salts of polyacrylic acid and poly(styrenesulphonic acid) shows a greater similarity with the latter group of salts.