The Absorption of Ultrasonic Waves in Liquids and its Relation to Molecular Constitution

Abstract

Measurements of the absorption of ultrasonic waves in water and ethyl alcohol were made by the pulse method, and are more accurate than those made by other methods. The absorption coefficient α in water was found to vary as the square of the frequency ν over a wide range of temperatures. The measurements in water were made at frequencies between 7.5 and 67.5 Mc/s. and temperatures between 0 and 95° c. The absorption decreased with increasing temperature by a factor of 8 between freezing and boiling points. The observed absorption was about three times that calculated from Stokes formula and this ratio was nearly independent of temperature. In ethyl alcohol measurements were made at 52.4 Mc/s., and at temperatures between - 50° and + 60° c. The absorption decreased by a factor of 3 in this range and observed values were about twice those given by Stokes' formula. Values of (α/ν2) at 25° c. are 22.0 x 10-17 sec2/cm. for water and 50.5 x 10-17 sec2/cm. for ethyl alcohol.