Browsing by Author "Okubo, Tsuneo"

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    Heat of Dilution of Aqueous Solutions of Polyacrylates
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1973, 69 (1), 1973) Ise, Norio; Mita, Kazuei; Okubo, Tsuneo
    The heats of dilution (AH) of aqueous solutions of polyacrylates having various gegenions, i.e., sodium and tetra-alkylammonium (alkyl = methyl, ethyl, n-propyl and n-butyl), were measured. The (A//) value of the sodium polyacrylate was negative in the investigated concentration range (0.005-0.17 mol dm-3), whereas those of organic salts were positive. With the addition of urea, the endothermicity was lessened. These results are discussed in terms of hydrophobic interactions between solute and solvent. The observed (A//) values were found to be in agreement with the values calculated by the theory of Lifson and Katchalsky, when an appropriate value of d In tz/d In 7Ts assumed (a is the ionic radius of rodlikc macroion and T the temperature). However, the assumed value for this parameter was in disagreement with that obtained directly from the partial molal volume measurements (by a factor of ~102).
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    Heat of Dilution of Aqueous Solutions of Sodium Carboxymethylcellulose and Sodium Polyacrylate
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (08), 1974) Mita, Kazuei; Okubo, Tsuneo
    The heats of dilution (A//) of aqueous solutions of sodium carboxymethylcellulose (NaCMC) having degrees of etherification of 0.75 and 1.4, were measured. Data for NaCMC at 25°C were in good agreement with Manning’s limiting law, whereas this was not the case for sodium polyacrylate (NaPA A) at 25°C. The AH values of NaCMC and NaPAA at 40°C were in agreement with the theory. It was found that Manning’s limiting law satisfactorily described the dependence of the AW of polyelectrolytes on the concentration, charge density, and temperature.