The Differences in the Time Lags of the Faraday Effect Behind the Magnetic Field in Various Liquids

Plane-polarized light from a zinc spark was passed through two liquid cells in succession. At the same time the current impulse through the spark passed, through leads of variable length, to oppositely wound solenoids surrounding the cells, where the magnetic fields rotated the plane of polarization of the light. By a proper adjustment of the positions of the cells and of the length of the lead wires it was possible to secure equal and opposite rotations of the plane of polarization in the two cells. Another liquid was then placed in one of the cells and its position changed until again the rotations were balanced. The distance the cell had to be moved, divided by the velocity of light, gave the difference in the time lag of the Faraday effect in the two liquids. The lag in carbon bisulphide behind that in hydrochloric acid was 0.3×{}10^-9 sec. The lags in the following liquids behind that in carbon bisulphide were found to be (in 10^-9 sec.): carbon tetrachloride 1.1; water 1.1; benzene 1.9; xylene 2.1; chloroform 2.4; toluene 2.5; amyl alcohol 4.0; bromoform 4.1. The precision of the results is about 0.3×{}10^-9 sec., depending somewhat upon the liquid.