HYDROGEN AND OXYGEN IN CONTACT WITH HOT SURFACES. 3 
platinum is enhanced by immersion in hot nitric acid, followed by a rapid washing 
with distilled water. The activity thus imparted is lost on exposure to the 
atmosphere, more quickly in damp than in dry weather, but may be restored either by 
ignition followed by rapid cooling, or by treatment with nitric acid. Finely divided 
silver was found to induce the combination of the gases at 150°, thin gold leaves 
at 260°, whilst fragments of non-metallic substances, such as charcoal, pumice-stone, 
porcelain, rock crystal and glass exhibited the power at temperatures below 350°. 
In the case of glass, it was observed that angular pieces were approximately twice as 
effective as spherical masses of equal surface. Dobereiner discovered that freshly 
prepared platinum black absorbs oxygen from the air, and when thus charged will 
cause the formation of steam when plunged into a jar of hydrogen. The operation of 
alternately charging the metal and then burning away the oxygen in hydrogen can, 
he found, be repeated many times. The platinum thus appeared to act as a carrier 
of oxygen to the hydrogen. # 
This conclusion was, however, criticised by FusiNiERif in 1825, who, on physical 
grounds, advocated the view that the function of the platinum is to condense the 
hydrogen on its surface. This view derived some support from the observation of 
William Henry;}; that when a platinum ball is immersed in a mixture of equal 
volumes of electrolytic gas and ethylene, the hydrogen and oxygen alone combine, no 
combination of the hydrocarbon occuring unless the original mixture contained a 
much larger proportion of electrolytic gas. This important result was confirmed by 
Graham in 1829.§ 
In 1834 Faraday|| found that if platinum electrodes are employed in the 
electrolysis of dilute sulphuric a.cid, the anode acquires the power of inducing the 
combination of electrolytic gas to a very high degree, whereas the cathode only 
becomes feebly active. He attributed the activity of the metal to its power of 
condensing the hydrogen and oxygen on its surface; the “condensed” gases then 
combine at the ordinary temperature. This theory was strongly opposed by 
I)e la Hive,^! who revived the idea that the metal acts simply as a carrier of oxygen 
to the combustible gas, the catalytic process being essentially a series of alternate 
oxidations and reductions. In support of the “oxygen” theory, he urged the fact 
that when an alternating current is sent through acidulated water between platinum 
electrodes, the latter become covered with a fine black powder, produced by the 
repeated oxidation and reduction of the metal. He further showed that platinum 
foil rendered active by any of Faraday’s methods will absorb oxygen but not 
hydrogen. 
* ‘Liebig’s Annalen,’ XIV. (1835), p. 10. 
t ‘Giorn. di Fisica,’ VII. (1824), pp. 133, 371, 443; VIII. (1825), 259; IX. (1826), p. 46. 
f ‘Annals of Philosophy,’ 1825, vol. 25, p. 416. 
§ ‘N. Quart. Journ. of Science,’ vol. 6, p. 354. 
|| ‘Experimental Researches in Electricity,’ I., p. 165; ‘Phil. Trans.,’ 1834, Part I., p. 55. 
U ‘ Pogg. Annalen,’ 46, 489 ; 54, 386. 
B 2 
