The Iodine Sorption Test. Factors Affecting Reproducibility and a Semimicro Adaptation

The iodine sorption test is a convenient though empirical method of measuring cellulose accessibility, but results show considerable variability. The relative importance of some experimental factors with respect to reproducibility of test results was, therefore, examined. Agitation during equilibration and use of a standard concentration of iodine solution and a standard sample weight were shown to be important. A fixed shedule of equilibration times and some degree of temperature control are also necessary. No increase in precision was obtained by direct titration of iodine in the sample, compared to the usual indirect determination by titration of supernatant solution and blank. The procedure can be scaled down from the usual 300-mg sample to 60-mg samples without loss of precision.