PREFACE. 



The work recorded in this monograph, while apparently dealing with 

 several subjects, is in fact closely connected, in that it all bears directly 

 or indirectly on the present solvate theory of solution, which was pro- 

 posed in the Johns Hopkins laboratory about fifteen years ago. 



The work on the absorption spectra of solutions by Dr. Shaeffer and 

 Mr. Paulus, using the radiomicrometer, led to results of the same gen- 

 eral character as those obtained earlier by Dr. Guy and recorded in 

 publication No. 190 of the Carnegie Institution of Washington. Solu- 

 tions of some non-hydrated salts are about equally transparent with 

 pure water, except at the bottoms of the absorption bands, where the 

 solutions are more opaque. Solutions of hydrated salts are in general 

 more transparent than pure water. All things considered, we regard 

 this as the strongest evidence thus far obtained in favor of the solvate 

 theory of solution. 



The work of Dr. Smith, on the conductivity and dissociation of cer- 

 tain organic acids in water, is a continuation of that which has already 

 appeared in publication No. 170 of the Carnegie Institution of Wash- 

 ington. The investigation by Dr. Wightman and Mr. Wiesel, on the 

 conductivity of organic acids in alcohol, is a continuation of the work 

 which has been in progress in this laboratory for more than ten years 

 on the conductivity and dissociation of electrolytes in water as a sol- 

 vent. (See publication No. 170 of the Carnegie Institution of Wash- 

 ington.) While this investigation is only preliminary, results of interest 

 have already been obtained. 



Dr. Wightman, Dr. Davis, and Mr. Holmes made a very exhaustive 

 study of two simple salts in mixtures of alcohol and water, solutions in 

 mixtures of these solvents showing abnormal properties. 



The work by Dr. Davis and Dr. Hughes, on the properties of solu- 

 tions in acetone, was taken up because of the abnormal behavior of 

 acetone as a solvent. 



The investigation by Dr. Davis and Mr. Putnam, of ternary mix- 

 tures of glycerol, acetone, and water, had in mind the fact that glycerol 

 has a very high viscosity, water intermediate viscosity, and acetone a 

 very low viscosity. The viscosities and conductivities of solutions in 

 ternary mixtures of these solvents were studied. A general discussion 

 of the results obtained, bearing on the solvate theory of solution, 

 seemed desirable. The work as completed was published in a large 



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