With this indeed ended the hardest struggle which met us in the attempt to introduce the new sulfuric acid process into technical industry. It was, however, by no means the last contest. When the process came to be put in operation on a larger scale, new difficulties in purifying the gases appeared, whose cause was almost as problematical and unforeseen as those which have been already described.
When the pyrites-burners were used to their full capacity, fumes were formed which seemed to mock every effort at absorption. Their cause was finally found to be the presence of unconsumed sulfur in small quantities. Like the quickly cooled sulfuric acid fume, this sulfur proved exceedingly difficult to remove. But how could this unburned sulfur be detrimental, when in the contact-apparatus it would burn to sulfur dioxid and sulfur trioxid? The explanation rests in the fact that this sulfur fume again contains traces of arsenic. This also it was unconditionally necessary to remove.
A radical means for this was finally found in thoroughly mixing the gases while still hot, so that the combustion of the last trace of sulfur was ensured. This mixing was accomplished by the injection of steam, which was found to have other and not less important advantages. It especially served to dilute the concentrated sulfuric acid in the gases, so that they were no longer condensed in the preliminary cooling conductors, and hence the evolution of arsin was avoided; when finally condensed in the chief cooling apparatus which was made of lead, they were so much diluted that they ceased to corrode the metal. Furthermore the formation of hard dust-scale in the various conductors was prevented, and danger of these becoming stopped up was avoided.
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In closing this lecture I may be permitted to place before you what a development the sulfuric acid manufacture has enjoyed in our works alone, since the introduction of this contact-process. The annual production of sulfuric acid anhydrid has been:
| In 1888 | 18,500 tons. |
| In 1894 | 39,000 tons. |
| In 1899 | 89,600 tons. |
| In 1900 | 116,000 tons. |
For the accomplishment of such a work the powers of a single individual were naturally far too limited. It required the powerful assistance of an establishment like the Badische Anilin-und Soda-Fabrik, the keen and far-seeing direction of a Heinrich Brunck, the experience of a Gustav Jacobsen, and the intelligent help of distinguished engineers, to bring to a successful completion such results as those I have endeavored to describe in this lecture, and which stand as an honor to the industrial progress of our fatherland.
