26 POPULAR SCIENCE MONTHLY. 



but although great claims were made, no practical results fol- 

 lowed. 



The hopes of this period are well characterized in a letter which 

 was written by Clement-Desormes to Schneider in 1835, only four years 

 after Phillips' discovery. A portion reads as follows : 



I am convinced that within at the most a decade sulfuric acid will be made 

 upon a large scale without the use of lead chambers, nitric acid, or nitrates; do 

 not let your courage fail, but press forward to this important goal. 



Thus early was the goal definitely pointed out. ... In the year 

 1852 came the discovery of Woehler and Mahla, that the oxids of 

 copper, iron and chromium exert a similar catalytic action upon a 

 mixture of sulfur dioxid and oxygen, to that of platinum sponge and 

 platinum foil. The mixture of copper and chromium oxids was found 

 to be particularly active in this respect. This was followed by the 

 discovery of many other catalytic substances, such as 'spent' pyrites, 

 highly heated quartz, platinized pumice, platinized asbestos and 

 platinized clay. 



This second period in historical development is, like the first, 

 characterized by the attempt to solve the problem of the manufacture 

 of ordinary sulfuric acid without recourse to the chamber process. 

 These efforts, however, were crowned by no practical success, indeed 

 it was not found possible even to make fuming sulfuric acid cheaply 

 enough to compete with that obtained by the distillation of the iron 

 vitriol shales. 



We now come to the turning point of our subject, the work of 

 Clemens Winckler. By his experimental investigations he reached the 

 conclusion that for complete conversion into sulfuric acid, it was neces- 

 sary that the mixture of sulfur dioxid and oxygen should be in stoi- 

 chiometric proportions, that is, two volumes of the oxid to one of 

 oxygen and that all other gases, even oxygen in excess, exercised an 

 injurious effect upon the reaction. This mixture Winckler prepared 

 very simply by the decomposition of ordinary aqueous sulfuric acid 

 with heat, subsequently removing the water. In this manner, by combin- 

 ing the gases, he obtained sulfur trioxid or fuming sulfuric acid at will. 



This conception of the suitable conditions for the success of the 

 contact process seemed at that time exceedingly obvious, and well calcu- 

 lated to explain all the failures which had attended every attempt to 

 utilize the gases of the pyrites-burners by Phillips' process. Winckler's 

 work attracted great attention and for a long time dominated all 

 further experimentation in connection with the contact process. At 

 about this time a similar process for the manufacture of fuming acid 

 was discovered in Messel's works and was protected by patents. 

 Winckler also brought out a more advantageous method of preparing 



