EXP. Equivalent solutions (1 / 10 normal) of the three bases are introduced into three vertical tubes, containing electrodes connected, in parallel, with a lighting circuit and with small electric lamps. When the two electrodes in each of the three tubes are at equal distances from each other, the lamp connected with the potassium hydroxide solution glows most brightly, that connected with the barium hydroxide solution a little less brightly, and the lamp connected with the ammonium hydroxide solution does not glow at all—not enough current is carried through the ammonium hydroxide solution to heat the filament in the corresponding lamp sufficiently to make it red. Now, the current, for a given fall of potential, is proportional to the conductivity of a solution (p. 48) and, in the equivalent solutions[137] the conductivity depends on the proportion of charged particles (the degree of ionization) of the base. It is clear then, that ammonium hydroxide is very much less ionized than are the two other bases. [p078] The resistance in a tube may be reduced, and the conductivity increased, by reducing the distance through which the current must be carried, ‹i.e.› by bringing the electrodes closer together. In the solution of barium hydroxide, we find that we must reduce the distance between the electrodes to about five-sixths the corresponding distance in the potassium hydroxide solution before we obtain, approximately, as bright a lamp from the current passing through it, and in the case of ammonium hydroxide, we must bring the electrodes so close together that they almost touch, the distance being only one or two hundredths of the distance between the electrodes in the potassium hydroxide solution. For the degrees of ionization of the three bases we have, approximately, the relation α_{K} : α_{Ba} : α_{NH_{4}}:: ‹d›_{K} : ‹d›_{Ba} : ‹d›_{NH_{4}}, if we indicate by ‹d›_{K}, ‹d›_{Ba}, ‹d›_{NH_{4}} the distances between the electrodes in the three solutions when the lamps are of uniform brightness, ‹i.e.› when the same quantity of current passes through each solution. In this deduction, the conductivities of the bases at infinite dilution (Λ_{∞}) are taken to be the same, which is roughly true. The experiment gives us a rough measure of the relative conductivities and the relative degrees of ionization of the three bases. It shows that potassium hydroxide is somewhat more ionized than is barium hydroxide, in equivalent solution, and decidedly more than is ammonium hydroxide.