The Crystalline Structure of Cellulose as Revealed by Acid Hydrolysis

The hydrolysis of holocellulose from Eucalyptus regnans F. v. M. has been studied employing a percolation technique and using 2 per cent. sulphuric acid for varying times of hydrolysis (0 to 6 hr.) and at three temperatures, 150, 160, and 170 �C. For comparison a series of experiments at 160 �C. on cotton was also carried out. The course of hydrolysis of the resistant cellulose in each experiment could be represented by the equation for a fist order reaction. The " reaction constant " for cotton was smaller than that for holocellulose. Powder X-ray diffraction photographs were made of samples at each stage of hydrolysis in the 160 �C. series. From these photographs the breadth at half maximum intensity of the line corresponding to the (002) planes, and the combined lines corresponding to the (101) and (101) planes was determined by photometric measurement. Throughout the period of hydrolysis studied, the line breadths decreased for both holocellulose and for cotton. This observation is considered to indicate the existence of a distribution of the degree of lateral order of the crystalline regions in each sample. The narrow line breadths in the cotton series' may indicate the existence of greater lateral order in the cotton than in the wood holocellulose and may account for the observed smaller reaction constant for cotton. The results obtained are consistent with the view that the mesomorphous regions surrounding the micelles are more extensive in wood holocellulose than in cotton.