Simplified volumetric determination of alpha, beta, and gamma cellulose in pulps and papers

Abstract

A relatively rapid and simple method for the determination of alpha, beta, and gamma cellulose is described. The method ordinarily employs a O.3-g sample, which need not be weighed accurately, but a O.03-g sample also gives fair results. Neither ash nor moisture determinations are involved, in fact, no precision weigh-ings are made. The cellulose is oxidized by potassium dichromate solution, the strength of which need not be known accurately, as the concentrations of the oxidimetric solutions do not enter into the calculations. The volumetric results are in good agreement with those of a gravimetric method, and are as reproducible, for widely different materials. The actual working time for four complete deter-minations is 1~ to 2 ?~ hours. Fundamental facts recently found concerning the separation of the cellulose fractions have been incorporated in the method. A calculation based upon the volumetric and gravimetric data for alpha cellulose indicates that the pentosans in the pulps studied are distributed among the alkali-soluble and alkali-insoluble fractions in approximately the same ratio as cellulose. It was also found that the amount of beta cellulose which precipitates is dependent upon the temperature, and that the separation should be made without heating the acidified filtrate. CONTENTS Page I. Introduction ___ ___ ________ __ __ ______________ ___ ______ __ ___ ____ __ 333 II. Method in detaiL _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 336 1. Mercerization and filtration _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 336 2. Treatment of alpha cellulose _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 336 3. Treatment of the filtrate _____ _____ ____ ________ ____ ___ ______ ____ 337 (a) Beta plus gamma portion _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 33. 7 (b) Gamma portion _____ ____ ______________ _____ ________ ______ 337 III. Treatment of the values obtained _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 337 1. Calculation of the percentages of alpha, beta, and gamma cellulose_ _ 337 2. Calculation of the total cellulose content of the sample_ _ _ _ _ _ _ _ _ _ _ _ 338 IV. Experimental results and discussion _____________________________ ___ 339 1. Volumetric values for alpha cellulose compared with the gravimetric results __________ __________________________________ _______ __ 339 2. Volumetric results for beta and gamma cellulose _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 341