SULFURIC ACID. 25 



production, not of dilute acid only, as in the chamber-process, but of 

 the strongest acids and of sulfur trioxid itself. 



Historical. 



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 favor- 

 able 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, pre- 

 pared 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 cele- 

 brated 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, 



