If arranged in three groups of ten each, it is trebled with a proportional loss of intensity, until the grouping reaches six series of five each, when a maximum supply of the mixed gases is obtained from the voltameter.
In arranging the groups, all the zinc ends of each series are connected, and all the platinum ends are likewise joined by proper wires.
Sixth Experiment.
A plate-glass trough, containing a few grains of iodide of potassium dissolved in water with some starch, is quickly decomposed into its elements by placing in two platinum plates and connecting them with the wires of the voltaic battery. If the glass trough is divided in the centre with a bit of cardboard, the purple colour of the iodine and starch is shown very beautifully on one side, but not on the other, as iodine is liberated at one pole and the alkali at the other. (Fig. 185.)
Fig. 185.
a a. A glass trough containing the salt dissolved in water, and divided temporarily with a bit of cardboard, b. c c are the two platinum plates connected with the battery, and the shaded side is supposed to represent the liberation of the iodine.
Seventh Experiment.
Some solution of common salt coloured with sulphate of indigo and placed in the trough is decomposed into chlorine, which bleaches one side of the indigo solution, and the alkali liberated on the other does not affect it.