Alum Solution

Abstract

PERHAPS the following evidence of the practical superiority of potash alum solution to distilled water in adiathermancy, when the electric arc is the radiant and the “radiometer” a Crookes, may be of interest. The same glass-sided cell was used throughout, and the difference of voltage between the carbons (“Apostle”) was kept sensibly constant (40 volts) through the experiments. Between each observation on the liquids the radiation from the arc was observed unimpeded, save by the glass of the radiometer, as recorded below. The time was given by a metronome (previously examined for constancy) beating half-seconds. No lens was used.