The Romance of War Inventions / A Description of Warships, Guns, Tanks, Rifles, Bombs, and Other Instruments and Munitions of Warfare, How They Were Invented & How They Are Employed

by Thomas W. Corbin

that under those conditions the presence of the electricity is not in any way noticeable. When a molecule becomes ionized, however, one ion always seems to run off with more than its fair share of the electricity, the result being that one is electrified positively, like rubbed glass, while the other is negatively charged, like rubbed resin.

Thus, when the common salt is dissolved in water, two lots of ions are formed, one lot positively charged and the other lot negatively. Each molecule of salt consists of two atoms, one of sodium and one of chlorine: consequently, one ion is a chlorine atom and the other is a sodium atom, the latter being positive and the former negative.

Now the electrodes are also charged by the action of the battery. That connected to the positive pole of the battery becomes positively charged and the other negatively. The anode, therefore, is positive and the cathode negative.

It has been pointed out that two similarly charged bodies, such as two pieces of glass or two pieces of resin, repel each other, while either of these attracts one of the other sort. Hence we arrive at a rule that similarly charged bodies repel each other, while dissimilarly charged bodies attract each other.

Acting upon this rule, therefore, the anode starts drawing to itself all the negative ions, in this case the atoms of chlorine, while the cathode gathers together the positive ions, the atoms of sodium. Thus the action of the battery maintains a sorting out process by which the sodium is gathered together around one of the electrodes and the chlorine round the other.

Those ions, by the way, which travel towards the an-ode are called an-ions, while those which go to the cath-ode are termed cat-ions.

Thus far, I think, you will have followed me: the chlorine is gathered to one place and the sodium to the other. The former creates bubbles and floats up to the surface and escapes. But where, you will ask, does the hydrogen come from, which we found, in the experiment, was bubbling up round the cathode. Moreover, what becomes of the sodium?

Both those questions can be answered together. The sodium ions, having been drawn away from their old partners the chlorine ions, are unhappy, and long for fresh partners. They therefore proceed to join up with molecules of water. But water contains too much hydrogen for that. Every molecule of water has two atoms of hydrogen linked up with one of oxygen, but sodium does not like two atoms of hydrogen: it insists on having one only. Accordingly the oxygen atom from the water, together with one of the hydrogen atoms, join forces with the sodium atom into a molecule of a new substance, a most valuable substance in many manufactures, called Caustic Soda, while the odd atom of hydrogen, deprived of its partners, has nothing left to do but to cling for a while to the cathode and finally float up and away.

The sum-total of the operation therefore is this: when we pass an electric current through salt water, between graphite electrodes, chlorine goes to the anode and escapes, while caustic soda is formed round the cathode and hydrogen escapes. Let us see now how this is applied commercially.