but although great claims were made, no practical results followed.
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:
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 necessary that the mixture of sulfur dioxid and oxygen should be in stoichiometric 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 combining 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 calculated 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