Popular Science Monthly Volume 65.djvu/397

Exported from Wikisource on September 25, 2024

ELECTROLYTIC DISSOCIATION.

393

silver and chlorine compounds as are in a measurable degree decomposed into silver and chlorine ions. Ostwald has treated this question comprehensively, and in this way

FIG. 7.

he has given a rational exposition of the general phenomena of analytical chemistry. To this fact belong, also, the poisonous effect of some salts; this effect may be considered as a special physiologically chemical reaction of the chemical compounds. On this point there are many valuable researches by Krönig and Paul, Clarke and others.

A property that is of physical character, but is much used by the analytical chemist, is the color of the solutions. It has been subjected to a rigorous research by Ostwald. At first we will trace how a compound, e. g., fluoresceine, H_12C_20O^5, behaves if one replaces its hydrogen atoms by other atoms, e. g., metals, iodine, bromine or atomic groups (NO_2). The curves in the next figure (Fig. 7) indicate absorption bands in the spectra of the corresponding compounds. A replacement of K_2 for H_2 in the fluoresceine itself alters the absorption-spectrum in a most sensible manner. This depends upon the property that the fluoresceine is dissociated to a slight extent, which is in striking contrast

FIG. 8.

FIG. 9.

to the permanganic acid which will be discussed immediately. Instead of a single absorption-band in the blue in the first case, we find two absorption-bands in the blue-green and the green part of the spec-

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Table of Contents

Title page

Popular Science Monthly Volume 65.djvu/397

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