VOL.7, NO.7
PRIZE-WINNING COLLEGE ESSAYS
1579
EXPERIMENT TO SHOW THE REMOVAL OF IONS IN DOUBLE DECOMPOSITION* FRANK D. MCCLELLAND, PIKEVILLB COLLEGE, PIRBVRLE, KENTUCKY The removal of ions from solution in neutralization, and in double decomposition in which a precipitate is formed, may be clearly shown in the following very simple demonstration. Into an ordinary conductivity cell in which the decomposition of the electrolyte is indicated by the glowing of an electric lamp, introduce a solution of barium hydroxide and a few drops of phenolphthalein solution. Close the switch and show the presence of a large number of ions by the bright glowing of the lamp. Add very dilute sulfuric acid (1:lOO) slowly with stirring, the lamp gradually dimming until it finally ceases to glow a t the same instant that the pink coloration disappears, indicating the complete removal of ions. The experiment may be repeated with a saturated solution of silver sulfate and a dilute solution of barium chloride, without the phenolphthalein, of course. This demonstration has proved useful in elementary and general chemistry classes, and has been found especially effectivewhen used to accompany a blackboard formulation of the ionic equilibria involved, as follows: Ba(0H). Ba++ H2S04 % SO
