Page:Popular Science Monthly Volume 60.djvu/487

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THE PROGRESS OF SCIENCE.

Amherst College party in charge of Professor Todd was at Singkep, where the sky was very unfavorable. At Mauritius the English astronomers had a fair sky. This eclipse well illustrates the importance of a large number of stations scattered along the belt of totality, for in spite of the clouds which widely prevailed the results from the stations, as a whole, are very satisfactory and will encourage similar efforts at coming eclipses.

THE SPECTRUM OF LIGHTNING.

Very wide interest has been taken in the spectrum of lightning, photographs of which have been obtained at the Harvard College Observatory. These were made by pointing a telescope, provided with an objective prism toward a portion of the sky where lightning was particularly bright. The spectrum is not always the same. Many of the lines appear to be due to hydrogen. The first line is a broad, bright band, extending from wave-length 3,830 to 3,930, and may be identical with the nebular line 3,875. The spectrum of lightning is curiously like that of the new star in Perseus, and other new stars. Now that the method of obtaining such photographs has been shown, it would seem possible to obtain a large number of them, taken under different conditions for a more complete study of the subject.

THE MANUFACTURE OF SULFURIC ACID.

Of all the products of chemical industry, sulfuric acid has always held the first place, and its importance increases yearly, since there is hardly a branch of manufacture in which it is not largely used. Its manufacture by the lead-chamber process has been universal until within a few years. This requires a large plant and the acid obtained is dilute. For many purposes this must be concentrated at no inconsiderable expense. Vessels of platinum are very generally used and a single still may cost upwards of $10,000. With the development of the coal-tar industry in Germany, and especially in connection with the rapidly increasing manufacture of artificial indigo, has come a demand for the more concentrated acid in large quantities.

That under the catalytic action of finely divided platinum, sulfur dioxid can be burned to sulfur trioxid, which with water gives sulfuric acid, has been known for nearly three quarters of a century, and in 1831 a patent was secured in England for the manufacture of the acid by this process. But in spite of vast amounts of effort devoted to it, and by some of the world's most distinguished chemists, this has never been made a practical success. Under the stimulus of the demand of the color factories of Germany, this problem has been very actively attacked in the past few years by their chemists, and at last the efforts have been crowned with the desired reward.

This work has been chiefly carried on under the auspices of the Badischen Anilin- und Soda Fabrik at Ludwigshafen. Theoretically the process is a model of simplicity. The gases from the pyrites burners, consisting chiefly of sulfur dioxid, oxygen and nitrogen from the air used, are, after purification and cooling, led through cylinders containing plates on which a contact mixture, with platinum as one of its constituents, is placed. The sulfur dioxid burns with the oxygen present in the gas, giving the trioxid, which is absorbed in a dilute acid. The acid obtained may be pure sulfuric acid, or may contain an excess of the trioxid—the fuming or Nordhausen acid. Several years of most patient investigation were, however, required before the conditions were discovered by which the process could be kept in continuous operation, there being a great tendency for the platinum mixture to cease its work after a few days' or even hours' use. This was due to the presence of