X-Ray Absorption Coefficients of Carbon, Hydrogen and Oxygen

Absorption coefficients of water and six organic liquids for x-rays of wave-lengths 0.2 to 0.98 A.—A large accurate spectrometer was used to disperse the rays from a Coolidge tube, whose current and voltage were kept constant within 0.1 per cent., and the beam entering the ionization chamber was so narrow that the range of wave-length included was only from 1.7 to 3 per cent. of the mean. The absorption cells, either 1 cm. or 10 cm. deep, were placed 10 cm. in front of the ionization chamber; therefore the absorption measured includes scattering. The variation with wave-length, at least between 0.35 and 0.98 Å., was found in all cases to be in accordance with the equation $\mu =A+B{\lambda }^3$, where for water, benzene, toluene, xylene, mesitylene, heptane and cyclohexanol the values for $A$ are 3.5, 15.3, 19.0, 21.7, 24.2, 21.5 and 20.5, respectively, and those for $B$ are 44.5, 74.9, 85.3, 98.3, 113.6, 87.3 and 121.0, respectively. These values give the coefficients for a gram molecule of each liquid in a cell 1 ${\mathrm{cm}.\mathrm{}}^2$ in cross section.