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Comparison of Carboxyl-Content Determination in Cellulose Half-Acid Ester Derivatives by Calcium Acetate and Silver Absorption MethodsDepurtment of Textile Chemistry, North Carolina State University, Raleigh, North Carolina 27650, U. S. A.
Depurtment of Textile Chemistry, North Carolina State University, Raleigh, North Carolina 27650, U. S. A.
Depurtment of Textile Chemistry, North Carolina State University, Raleigh, North Carolina 27650, U. S. A. Carboxyl content of cellulose half-acid ester derivatives was determined by the calcium acetate method and by the absorption of silver from silver meta-nitrophenolate solutions. Both methods utilize the acidity of the carboxyl proton in an ion-exchange reaction, thereby producing a salt. With both the calcium acetate and the sitver absorption methods, the neutralization of the carboxylie acid groups is incomplete below pH 6.5. Tp compensate for this effect, a correction curve was derived for cellulose half-acid ester derivatives, which agreed fairly closely to a curve previously derived for cellulose half-acid etlter derivatives. No correction curves could be accurately applied to the silver-absorption test, but 0.6 g was selected as the optimum sample size because larger sample sizes usually resulted in a decrease in the carboxyl determination due to lowering of pH and/or exhaustion of the silver, which had orfly limited solubility. Nevertheless, the free degree-of-substitution values obtained with the calcium acetate method, using the new correction curve, and with the silver absorption method utilizing 0.6 g samples, differed on the average by only 0.011.
Textile Research Journal, Vol. 49, No. 6,
352-359 (1979) |
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