Hemicelluloseに關する研究

Abstract

In the present studies on the samples of polyuronide hemicellulose prepared from elm, beech, and cherry woods, comparative estimations of the carboxyl groups by the carbon dioxide evolution, calcium acetate and potentiometric titration methods were carried out in order to ascertain whether the carboxyl groups in the molecules are free or bound, and simultaneously, whether the caictium acetate or potentiometric titration methods is applicable in estimating carboxyl groups quantitatively. The results are summerized as follows: (1) The acid decomposition with 12% HCI for 5 hours makes the evolution of carbon dioxids completely quantitative from glucuronic acid residus of the sample. (2 ) Gocd agreement is obtained between the carboxyl values found by the potentiometric titra-tion in presence of NaBr and by the calcium acetate method for every sample, but these values are smaller than the theoretical values calculated from the quantiites of carbon dioxide evolved by acid decomposition. (3) From this difference, it would seem reasonable to assume that all carbovyl groups in the pclyuronide hemicellulose are not free, and that a limited amount of bound or potential carboxyl, at least, may be in the form of intermolecular anhydride or ester groups or as intramoleculai lactone.