Returning to our glass, let us suppose that the bottom has been so
perforated that two little strips of platinum wire can be inserted side
by side, at the distance of half an inch from each other, and so as to
leave the tumbler water-tight. Now attach the lower ends of these wires
to wires connected with the poles of an ordinary galvanic battery. Small
bubbles will be seen to rise immediately around the wires in the water.
Fill two glass tubes (closed at one end) with water, and having placed
a little piece of paper over the top, hold the finger on the paper, and
quickly invert the tubes over the wires. The escaping gases will thus be
secured. The electric current is counteracting the affinity of the two
elements that form water, and they are collecting in the tubes. You will
soon find that the H gathers more rapidly than the O, and upon measuring
them there will be twice as much of the former as of the latter. Weigh
them, and the O outweighs the former eight times. If, then, one atom of
O weighs eight times as much as two atoms of H (H₂O is the symbol for
water, remember,) then one atom of O weighs sixteen times as much as one
atom of H; or, in other words, H is sixteen times lighter than O, and is
the lightest substance known.
Place the O and H in a eudiometer over mercury, and send an electric
spark through them; the gases will disappear, with a loud explosion, and
there, resting on the quicksilver, will be seen the original drops of
water which we decomposed. We have now shown the composition of water,
both by analysis and synthesis.