Absorption Coefficients of Various Organic Liquids for X-rays of Wave-length 0.715 Å.—By means of a spectrometer with narrow lead slits and a calcite crystal, the ${\mathrm{K}}_{\alpha }$ radiation from the Mo target of a Coolidge tube was reflected into an ionization chamber, and the effect of interposing a cell containing a known thickness of liquid before the first slit, was measured. Thus absorption coefficients were determined for carefully purified samples of pinene (${\mathrm{C}}_{10}$${\mathrm{H}}_{16}$), limonene (${\mathrm{C}}_{10}$${\mathrm{H}}_{16}$), benzene (${\mathrm{C}}_6$${\mathrm{H}}_6$), toluol (${\mathrm{C}}_7$${\mathrm{H}}_8$), isopropyl alcohol (${\mathrm{C}}_3$${\mathrm{H}}_8$O), methyl proprionate (${\mathrm{C}}_4$${\mathrm{H}}_8$${\mathrm{O}}_2$), ethyl acetate (${\mathrm{C}}_4$${\mathrm{H}}_8$${\mathrm{O}}_2$), acetone (${\mathrm{C}}_3$${\mathrm{H}}_6$O), ethyl formate (${\mathrm{C}}_3$${\mathrm{H}}_6$${\mathrm{O}}_2$) and trimethylene glycol (${\mathrm{C}}_3$${\mathrm{H}}_3$${\mathrm{O}}_2$).

Atomic absorption coefficients for C, H, and O for X-rays of wave-length 0.715 Å. were computed from the above data, assuming absorption to be an additive atomic property, and came out from 11.00 to 11.55 × ${10}^{-24\mathrm{}}$ for C, 0.45 to 0.50 × ${10}^{-24\mathrm{}}$ for H and 29.9 to 31.0 × ${10}^{-24\mathrm{}}$ for 0. Using the mean values, the computed coefficients are within $\frac{1}{3}$ per cent. of the observations, on the average. But the fact that the computed values for acetone and water are 1 per cent. too low suggests that the assumption that absorption is an atomic property may not be accurately true.

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