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.
For the production of Chlorine the apparatus need be little more than our experimental apparatus made large. The anode can be covered in such a way as to catch the gas as it bubbles upwards. In times of peace this gas is chiefly used for making bleaching powder. It is led into chambers where it comes into contact with lime, with which it combines into chloride of lime, a powder which is sometimes used as a disinfectant, but the chief use of which is for bleaching those cotton and woollen fabrics for the manufacture of which this country is famous throughout the world.
The Germans, however, have taught the world another use for chlorine. Those gallant Canadians who were the first victims of the attack by "poison gas" who suddenly fo