Triumphs and Wonders of the 19th Century: The True Mirror of a Phenomenal Era / A volume of original, entertaining and instructive historic and descriptive writings, showing the many and marvellous achievements which distinguish an hundred years of material, intellectual, social and moral progress

by James P. Boyd

IV. ANALYTICAL CHEMISTRY.

No branch of chemical science has a more general interest for the public than that which relates to the determination of the materials of which bodies are composed, and the proportions in which they exist.

At the beginning of the century considerable progress had been made in this branch of knowledge by the researches of Boyle (1626–1691), Hoffmann, Margraff (1709–1780), Scheele and Bergmann (1735–1784). Berzelius, as has already been mentioned, had added a new and valuable factor to chemical analysis by the development of the blowpipe, and in the early part of the century mineral analysis was still further advanced by Klaproth (1743–1817), Rose (1798–1873), and many others.

No one man did so much to advance this branch of chemical science as Fresenius (1818–1897). He collated and proved all the proposed methods of analysis, both qualitative and quantitative, and out of a confused mass of material formed a logical system of procedure, which has proved invaluable to the progress of chemical science in all its branches.

The volumetric methods of analysis, which save so much time and labor without sacrificing accuracy, were developed by Gay-Lussac, Vauquelin (1763–1879), Mohr (1806–1879), Volhard, Sutton, Fehling, and Liebig.

The methods of gas analysis have been worked out chiefly by Bunsen, ably assisted by Winkler and Hempel.

The methods of determining the elementary bodies in organic compounds have been developed by Dumas, Liebig, Will, Varrentrap, and Kjeldahl, to the last of whom chemical analysis owes a debt of gratitude for the invention of a speedy and accurate method of determining nitrogen.

Not much less is the debt due to Gooch for the invention of the perforated platinum crucible, carrying an asbestos felt for securing precipitates by filtration, in a form suitable to ignition without further preparation.

WILLIAM CROOKES, F. R. S.

Through the classic researches of Arago (1786–1853) and Biot (1774–1862), polarized light has been made a most valuable adjunct to chemical research, serving as it does to measure the quantity of various alkaloids, essential oils, and sugars.

Based on these researches of Biot and Arago, Ventzke, Soleil, Scheibler, Duboscq, Landolt, and Lippich have constructed apparatus, which have made an exact science of optical saccharimetry. Optical analysis is not without its relation to theoretical chemistry, for by it has been proved the assumption that optically active bodies contain an asymmetrical carbon atom,—that is, one which combines with four different atoms or radicles.

Electricity has become also one of the most useful factors in chemical analysis. Many metals are easily deposited by electrolytic action, and their separation and determination rendered easy and certain.

Chemical analysis has not only given us accurate knowledge of the constituents of matter, but by revealing the deportment of molecules and groups of molecules in inorganic and organic compounds, has opened up a path for organic and synthetic chemistry which otherwise must have remained forever closed.

The discovery and development of spectrum analysis is one of the great achievements of the nineteenth century in chemical science.

Wollaston, in 1802, first noticed that the spectrum of the sun’s light, when greatly magnified, was not composed of colors gradually changing from one to the other, but that the continuity of the colors was interrupted by dark bands. Fraunhofer, in 1814, had made a map of the solar spectrum, showing 576 of these dark lines. Fraunhofer was entirely ignorant of the cause of these dark lines, but when he had found them, not only in the light from the sun, but also from the moon and the fixed stars, he properly concluded that they were due to something entirely independent of the earth.

It remained for Bunsen and Kirchhoff, in 1860, to point out the fact that these dark lines were characteristic of certain chemical elements existing in the sun and its photosphere, and this fact is the foundation of spectrum analysis. The broad black band in the sun’s spectrum, called by Fraunhofer D, corresponded exactly in position and in width with the yellow band produced by a flame containing incandescent sodium. There was no doubt whatever, therefore, that the two phenomena were due to the same cause; but why in the one case should the band be black and in the other yellow? This question was answered by the discovery of the fact that a ray of light colored by incandescent sodium, passing through a luminous atmosphere of the same metal, would lose by absorption all of its yellow color, and would display a black band where before the yellow color existed.

Based upon this observation, the development of spectrum analysis went forward with amazing rapidity. The hundreds of lines in the sun’s spectrum were found to occupy exactly the position of luminous lines in the spectra of various metals, and thus it was possible for the chemist to extend his investigations beyond the limits of the earth, and distinguish the chemical elements in the sun and in the fixed stars billions of miles farther away from us than the sun itself. Celestial chemistry has thus become a fixed and definite science.

But the value of spectral examinations has extended still farther. Many luminous lines were observed in the spectrum which were not found in the spectra of any known element. The inference then logically arose that there were elements yet undiscovered to which these lines were due. From this starting point investigations proceeded which have led to the discovery of a large number of elementary bodies. Among the important elements that have been discovered by means of spectrum analysis may be mentioned: cæsium, rubidium, thallium, indium, gallium, ytterbium, and scandium.

Spectrum analysis is also extremely useful in proving the verity of supposed new elements; for if a supposed new element should be found to give a series of spectral lines coincident with those already known, it would be a positive proof of the fact that the supposed new element was but a mixture of bodies already known to exist.