The Romance of Modern Chemistry

HOW FIRE IS MADE some substances have in promoting a chemical action without themselves being altered thereby. The platinum, for instance, which induces the hydrogen and oxygen to combine so readily, is found to be unchanged at the end, and this is the case also in other processes where finely- divided platinum behaves as a catalytic agent. Its action has evidently something to do with the very large surface which is exposed by the porous, finely-divided metal, but opinions differ as to the correct explanation. Some think that the gases condense in the surface of the platinum, and are thus brought into closer contact—the platinum surface acting as a sort of birdlime for the flying mole- cules; others consider that the platinum first lays hold of the oxygen molecules to form a compound, and then meekly delivers them over to the hydrogen, with the net result that water is formed, and the platinum is left as it was at the beginning, with nothing to show for its labour. Although Dobereiner’s lamp has gone out in more senses than one, there are some modem devices based on the same principle. Many incandescent burners used to be provided with a little piece of platinum above the jet, so that when the gas was turned on, it would light without the help of a match. This arrangement has gone out of use now, largely because the platinum rapidly deteriorates in efficiency and finally loses its power of igniting the gas. Another piece of apparatus, based on the same principle, is a cigar-lighter which is sold at the present time. This consists of a small metal vessel provided with a cap; the vessel holds some volatile spirit, and attached to the cap there is a piece of very fine platinum wire. When this is held in the vapour of the spirit, 126