By the use of two constant deviation spectrometers in series and a Coblentz linear thermopile, the absorption coefficient of water was measured for various temperatures from 0° to 95°C. The bands found showed maximum absorption at the following wave-lengths There is a shift toward shorter wave-lengths as the temperature increases and also a marked increase in magnitude of the maximum absorption for the bands at.77,.98 and $1.21\mu$. These changes are qualitatively explained by Roentgen's hypothesis that water is a mixture of at least two kinds of molecules, presumably ${\left({\mathrm{H}}_2\mathrm{O}\right)}_2$ and ${\left({\mathrm{H}}_2\mathrm{O}\right)}_3$, whose relative amounts change with a change of temperature.

• Received 25 August 1925

DOI:https://doi.org/10.1103/PhysRev.26.771