Page:Popular Science Monthly Volume 61.djvu/31

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production, not of dilute acid only, as in the chamber-process, but of the strongest acids and of sulfur trioxid itself.



In the historical development of the contact-process we recognize four periods, the first of which was ushered in by the discovery in 1831 by Phillips of the catalytic action of platinum in the manufacture of sulfuric acid. The second period dates from the discovery by Woehler and Mahla, in 1852, of a similar catalytic action on the part of a number of other substances, and the explanation of the mechanism of the reaction in some of these cases. The third period, which begins with Winckler, is characterized by the use of certain gaseous mixtures which, according to the conception of that time, were especially favorable for the reaction from a quantitative standpoint. In the fourth period there is a return to the use of the gases from the pyrites-burners. As their ultimate goal, the early efforts, like those of the present period, seek by the aid of the catalytic process, entirely to replace the lead chambers in the manufacture of ordinary sulfuric acid, while the workers of the third period, profiting by the large number of earlier failures, confined themselves to the attempt to make the expensive fuming acid.

The discoverer of the catalytic action of platinum in general was Sir Humphry Davy, who found that when a heated platinum wire was brought into a mixture of oxygen or air with hydrogen, carbon monoxid, ethylene or cyanogen, it became red hot, and the gas mixture was burned, generally slowly, but sometimes with great rapidity. Three years later Edmund Davy discovered that finely divided platinum, prepared by evaporating the nitrate and treating the residue with alcohol, was brought to a glow by moistening with alcohol, the alcohol itself being ignited. Doebereiner found in 1822 that the residue left on heating ammonium platinum chlorid, acted in the same manner, and in 1823 he discovered that when a stream of hydrogen impinged on finely divided platinum, it took fire. The next year he brought out the celebrated Doebereiner lamp, which depended on this phenomenon.

The honor of having applied this catalytic action of platinum to the manufacture of sulfur trioxid belongs, as has already been said, to Peregrine Phillips, Jr., a vinegar-maker of Bristol. In 1831 he received an English patent for his discovery. This discovery of Phillips' was confirmed in 1832 by two distinguished German scientists, Doebereiner and Magnus. Seventeen years passed with no further developments, and then the Belgian chemist, Schneider, announced that he had solved the problem of manufacturing sulfuric acid without the aid of lead chambers. He believed that he had found in a specially prepared pumice-stone a catalytic substance of extraordinary activity,