Two x‐ray methods have been developed for determining the crystallinity of cellulose using a Geiger counter spectrometer. The two methods were applied to six native cotton varieties, to a cross‐bred variety, and to two cottons chemically modified with ethylamine. The x‐ray scattering curves for each of the nine samples were compared with those from a highly crystalline sample, a cotton hydrolyzed in HCl, and an amorphous cotton sample to provide a relative measure of crystallinity, or crystalline index.
With fully corrected data the average crystalline index of the six cotton varieties was found to be 68.3 and 78.7% by the correlation and by integral methods, respectively. The crystalline indices of the remaining samples determined by the correlation and by the integral methods are, respectively, cross‐bred cotton (S×P), 54.3 and 77.2%; cotton treated with anhydrous ethylamine, 29.7 and 50.9%; and cotton treated with 75% aqueous ethylamine, 28.3 and 50.3%.