The Effect of certain Dissolved Substances on the Infra-Red Absorption of Water

Abstract

Infra-red absorption spectra of aqueous solutions of sixteen inorganic compounds from 0.8 to 2.3 μ, have been determined to see how the dissolved substances affect the absorption of the water. Care was taken to eliminate stray light by using two constant deviation glass spectroscopes in series. Readings were taken alternately with a cell containing a solution and with one containing water. Curves were thus obtained for the alkali hydroxides, five chlorides (Al, Ca, Mg, Na, Sr), five nitrates (Ag, Al, Mg, N$H_4$, Zn) and three sulphates (Ag, Na, Zn). (Figs. 3-16). All solutes decreased the absorption in the water band at 1.44μ and probably also in the band at 2μ, whereas all excepting ${\mathrm{Al}}_2$ ${\left(\mathrm{S}{\mathrm{O}}_4\right)}_3$, ZnS${\mathrm{O}}_4$ and the hydroxides increased the absorption in the bands at 0.97 and 1.2μ. These results do not agree with the solvate theory which ascribes the effect to the formation of hydrates, since some non-hydrating compounds decreased the absorption at 1.44μ.