Page:Popular Science Monthly Volume 61.djvu/30

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HAT the subject on which you ask me to speak is of the greatest interest from an industrial standpoint needs no argument. The sulfuric acid industry is rightly looked upon as the foundation of inorganic 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 disposal it would be of course impossible to treat exhaustively the great mass of material bearing on the subject, and hence I must confine myself 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 interesting 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 slowness, and therefore every effort has been made from an industrial standpoint 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