Dispersion of the Velocity and Anomalous Absorption of Sound in Hydrogen

The velocity and absorption of sound in hydrogen were measured at frequencies of 3.855 Mc and 6.254 Mc and pressures of 1.00, 0.83, 0.67, and 0.50 atmos., with all observations made at 25°C. Dispersion of the velocity from 1321.9 m/sec. to 1382.0 m/sec. and anomalous absorption which were observed are interpreted as caused by molecular absorption induced by loss of the rotational degrees of freedom. Calculations place the inflection point of the dispersion curve at 10.95 Mc and the peak of the absorption curve at 10.0 Mc from velocity data, and at 16.1 and 14.8 Mc from absorption data. The relaxation times for pressures of 1 atmos. from the two sets of data are 1.9 and 1.7×${10}^{-8\mathrm{}}$ sec. The $\frac{f}{p}$ law is not strictly obeyed.