280 CARNEGIE INSTITUTION OF WASHINGTON. 



The following rather surprising result was obtained : Pure water of 

 a certain depth of layer was found to be more opaque for certain 

 wave-lengths than an equal depth of water in a solution of a salt like 

 calcium chloride, while pure water had the same absorption as an 

 equal depth of water in a solution of potassium chloride. Why this 

 difference? 



Calcium chloride is a strongly hydrated salt, while potassium 

 chloride is scarcely hydrated at all; and this suggested a possible 

 explanation for this result. A number of strongly hydrated com- 

 pounds were studied, and also a number of compounds which com- 

 bine with very little of the solvent when they are dissolved in it. 

 The solvent was generally more opaque than the water in the solution, 

 whenever it was a solution of a strongly hydrated salt. Whenever 

 the salt was only slightly hydrated, the pure water and the water in 

 the solution had the same absorption. This would indicate that the 

 water combined with the dissolved substance had less, in general, 

 absorption than pure, uncombined water. The above fact is regarded 

 as evidence that there is combination between the solvent and the 

 dissolved substance. 



During the second half year the work upon the absorption spectra 

 of solutions by means of the radiomicrometer had to do with the 

 mapping of the infra-red spectra of solutions of salts of cobalt, 

 nickel, praseodymium, and neodymium. The results of all of this 

 work have been published as monograph No. 190 by the Carnegie 

 Institution of Washington. 



The study of the conductivity of solutions of salts in mixtures of 

 ethyl alcohol and water has been continued during the year by Dr. 

 E. P. Wightman, Dr. P. B. Davis, and Mr. August Holmes. They 

 made a careful and fairly exhaustive study of solutions of potassium 

 iodide and sodium iodide in the above-named solvents, both from 

 the standpoint of conductivity and of viscosity. Both the conduc- 

 tivity and viscosity methods were improved, and a new method 

 worked out for preparing the mixed solvents of a given concen- 

 tration of the one in the other. Several dilutions of potassium 

 and sodium iodides in the various mixtures were studied, and the 

 data obtained plotted in the form of curves. The presence of these 

 iodides greatly increases the viscosity of the mixed solvents, espe- 

 cially between 100 per cent and 60 per cent alcohol. It was found 

 that the conductivity of the salt continually decreases in passing 

 from pure water to pure alcohol. With rise in temperature there 

 is a breaking down of the slightly hydrated ion and a small in- 

 crease in the temperature coefficients of conductivity. In alcohol 

 the temperature coefficients are linear, which means that there is 

 little or no alcoholation. With rise in temperature both the con- 

 ductivity and fluidity curves tend to become more nearly linear. 



