Because vibrations have been found in liquids which closely resemble what have been regarded as lattice vibrations in crystals, we examine whether the vibrations in crystals are to be ascribed to local complexes rather than to an extended lattice. Our experiments confirm the appropriateness of the term ``lattice vibrations'' and analogous vibrations must, it seems, be accepted as taking place in solutions. Alcohol with a more regular arrangement within the liquid than water gives rise to greater sharpness in the quasi-lattice vibrations of the solution. Correspondingly, a mixed solvent gives a greater spread and diffuseness to the vibrations even though the electric fields immediately surrounding the positive ions in such a solution are as sharp in their effect on the electronic levels as in the pure solvents separately. With absolute alcohol, europium chloride and europium nitrate form solutions which show different quasi-lattice vibrations in their spectra; but when these salts are dissolved in water, the vibrations of the solutions appear about the same. The hydrated crystals of europium chloride exhibit lattice vibrations which are different from those of the hydrated mixed magnesium europium nitrate. In the ionic crystals of anhydrous europium fluoride, a lattice frequency appears; this is considerably greater than any yet measured. A discussion concerning the nature of the systems partaking in the quasi-lattice vibrations is included.
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