The changes in certain absorption spectra in different solvents

In recent years a considerable amount of attention has been given to the absorption spectra of inorganic salts, and some conclusions of somewhat startling significance have been drawn from the results. With the exception of a few cases, however, notably the recent work of Houstoun and his colleagues, this work has been qualitative, and in most cases has been carried out by photographic methods. The great disadvantages of these methods are now recognised, and it therefore becomes a matter of importance to discover whether accurate quantitative measurements will throw any further light on the subject. The object of the present investigation has been to select some characteristic substance and to make an accurate quantitative investigation of its absorption spectrum in different solvents. In the course of the work the question of the gradual replacement of one acid radicle by another has also been investigated, and an attempt had been made to investigate the possible effect of pressure on the absorption spectra of solutions. The choice of material is somewhat restricted, the absorption of most inorganic salts being somewhat ill-defined, except in a few isolated cases. After a number of preliminary investigations uranous chloride was chosen. It can be obtained pure, it is soluble in a large number of solvents, and the absorption bands, which are comparatively well defined, are chiefly situated in the orange-red and green parts of the spectrum, and are, therefore, particularly well suited for photometric measurements. The chemical properties of this substance have been fully investigated by Colani. Up to the present, with the exception of the work of Jones and Strong, only a few isolated measurements have been made on the absorption of this substance, the uranous salt having been in most cases prepared in solution by the reduction of the corresponding uranyl salt with zinc, a method obviously unsuitable for quantitative measurements. The uranous chloride and all other chemicals used in this investigation were obtained from Kahlbaum.