The Conversion of Starch into Dextrin by X-Rays

When solutions of starch are irradiated for several hours by X-rays of moderate penetrating power, the opacity and viscosity of the solutions are markedly diminished. These physical changes are attended by chemical changes; there is a partial conversion of the starch into soluble starch and dextrin. A quantitative estimation of the amount of dextrin formed after the starch solution had been irradiated for 8½ hours showed that it corresponded to about 5 per cent. of the amount of starch initially present. When solutions of dextrin were subjected to a similar exposure of X-rays, no conversion of this substance into glucose was obtained. From the fact that starch may be converted into dextrin by hydrolysis, a simple explanation of the effect would be afforded if water were decomposed by X-rays. From the negative results obtained by Kern baum on these lines, however, it seems as if the effect were more likely attributable to a direct action upon the starch molecules, either by the X-rays or the secondary rays which they produce.