24 POPULAR SCIENCE MONTHLY. 



SULFURIC ACID AND ITS MANUFACTURE BY THE 



CONTACT-PROCESS.* 



By Dr. R. KNEITSCH. 



THAT the subject on which you ask me to speak is of the greatest in- 

 terest from an industrial standpoint needs no argument. The sul- 

 furic acid industry is rightly looked upon as the foundation of inor- 

 ganic technology, but it has also in the last few years, aside from its 

 importance in so many departments of the various textile branches, 

 become of equal necessity in the manufacture of the organic dye-stuffs. 

 This is especially the case in the field of the alizarin dyes, and more 

 recently, as was shown just a year ago from this platform by Heinrich 

 Brunck, in the manufacture of synthetic indigo. If then in industries 

 of such importance a complete revolution is taking place, a description 

 of the discoveries and experiments which have made such a revolution 

 possible can not fail to be of interest. In the limited time at my dis- 

 posal it would be of course impossible to treat exhaustively the great 

 mass of material bearing on the subject, and hence I must confine my- 

 self chiefly to the results of the work which has been carried on at the 

 Badische Anilin und Soda-Fabrik. 



The chemistry of the sulfuric acid manufacture is exceedingly 

 simple, indeed chemistry seems at first sight to play but a subordinate 

 role. Nevertheless this simple process presents an exceedingly inter- 

 esting and important example of a gas reaction which occurs only at high 

 temperatures. The reaction between sulfur dioxid and oxygen, although 

 it is exothermic, takes place, as is well known, with extraordinary slow- 

 ness, and therefore every effort has been made from an industrial stand- 

 point to discover methods of hastening it by the use of catalytic 

 substances. Indeed the lead chamber process itself depends upon the 

 use of nitric acid and the lower oxides of nitrogen as such catalytic 

 agents. 



There are, however, many solid substances which have this same 

 catalytic action, though only at high temperatures, and which in virtue 

 of their state of aggregation suffer no loss in the process. These also 

 possess a further great advantage over their gaseous rivals, in that 

 their action goes on in the absence of water, thus rendering possible the 



* Lecture before the German Chemical Society, October 19, 1901. Trans- 

 lated into English by Professor Jas. Lewis Howe, Washington and Lee Univer- 

 sity. 



