Optical‐diffraction methods for deducing the effects of hydrogen atoms on X‐ray intensities

I n a re-investigation of the s t ructure of t r iphenylene (Taylor, 1954)* based upon the da ta of Klug (1950) there appeared to be some indicat ions of the hydrogen a toms on the (001) Fourier projection. These indicat ions were not par t icular ly clear, and there was some doubt whether the work involved in calculat ing the contribut ions of the twelve hydrogen a toms to all the hk0 reflexions would be wor th while. A compromise was reached b y using optical methods (Hanson, Lipson & Taylor, 1953) to decide which reflexions were mos t grea t ly affected, and the calculations were confined to these. The method used was as follows. First , the probable positions of the hydrogen atoms in the un i t cell were deduced from the known positions of the carbon a toms and an assumed value of 1.07 ~ for the C H distance (Cochran, 1953). A mask was made in which only these hydrogen a toms were represented, and the diffraction pa t t e rn was recorded; a representat ion of the most prominent features is shown in Fig. 1. B y laying the