Effect of Magnetic Field on the Propagation of Sound in Paramagnetic Liquids

The problem of the effect of magnetic fields on the velocity of sound in paramagnetic fluids is investigated with the help of the Phase-Comparison-Interferometer, which allows the detection of changes in sound velocity right up to about 1 mm/s. A transversal magnetic field up to 10⁴ G was used. Aqueous solutions of a uniform concentration of 1 molar each of the following substances were investigated: ferric chloride, manganese(II) sulphate, ferrous sulphate, cobalt(II) sulphate, nickel(II) sulphate, nickel(II) nitrate, potassium ferricyanide and cupric sulphate. The sound velocity is observed to decrease in the magnetic field, with magnitudes lying between 2 cm/s to about 50 cm/s at a field strength of 5000 G. Up to about 2000 G this change is very small, but increases rapidly at higher fields. In addition to change in the sound velocity, it appears that the absorption coefficient of sound also undergoes a change.