General Outline of the Investigation. 5 



somewhat revised form, for the sake of completeness and on account of 

 its close relation to the new material that is to be presented. 



I desire in this connection to express my great indebtedness to the 

 American Academy for the liberal grants made to me from the Rumford 

 Fund in the early stages of the work. 



During the past four years the work has been continued under the 

 auspices of the Carnegie Institution of Washington, and its progress has 

 been largely due to the assistance thus afforded. I have also been fortu- 

 nate in having had associated with me a number of able research workers, 

 by whom the work has been prosecuted on its different sides. 



With this apparatus and method in its original form, conductance and 

 specific-volume measurements were made by Dr. W. D. Coolidge and 

 myself with two substances, sodium and potassium chlorides, at various 

 temperatures between 26 and 306 and at various concentrations between 

 0.1 and 0.0005 normal. The results of these experiments are also pre- 

 sented in Part II. Since their original publication several corrections of a 

 minor character have been applied to the data. 



As was to be expected a number of important improvements in the 

 apparatus and method suggested themselves in the course of these experi- 

 ments, and these were subsequently worked out by Dr. Coolidge, who 

 presents a description of them for the first time in Part III of this publi- 

 cation. The method is now being further developed so as to adapt it to 

 still higher temperatures extending above the critical one, where a control 

 of the pressure, entire elimination of the vapor space in the bomb, and 

 measurements at small intervals of temperature will be essential. 



Mr. A. C. Melcher has made measurements with another salt of the 

 uni-univalent di-ionic type (silver nitrate), and has then extended the 

 investigation to salts of other types (potassium sulphate, barium nitrate, 

 and magnesium sulphate), at a series of temperatures up to 306, namely, 

 18, 100, 156, 218, 281, and 306. The results of these experiments, 

 as well as some additional ones with sodium and potassium chlorides, are 

 presented in Part IV. 



Dr. H. C. Cooper, Mr. Yogoro Kato, and Mr. R. B. Sosman have 

 studied the conductivity and ionization up to 218 of certain acids and 

 bases ; namely, of hydrochloric and acetic acids and of sodium and ammo- 

 nium hydroxides. They have also determined by conductivity measure- 

 ments the hydrolysis of sodium acetate at 218 and that of ammonium 

 acetate at 100, 156, and 218, and have calculated therefrom at these 

 temperatures the ionization-constant of water itself, upon which in large 

 measure the phenomenon of hydrolysis depends. This work is described 

 in Parts V, VI, and VII ; the share of each investigator being indicated 

 under the separate titles of these parts. Mr. R. B. Sosman has made an 

 entirely similar series of measurements at 306 with ammonium hydroxide, 



