4 Conductivity of Aqueous Solutions. Part I. 



It was not, however, primarily the direct value, however great, of the 

 physical and chemical constants of specific substances at high tempera- 

 tures that led to this investigation, but rather the hope that, by determining 

 them under widely varied conditions of temperature and pressure, general 

 principles might be established relating to the influence of these factors on 

 the migration-velocity of ions, on the ionization of dissolved substances of 

 different types and of water itself, on the hydrolytic dissociation of salts 

 of weak acids or bases, and on the solubility of substances, and that rela- 

 tions might be shown to exist between some of these properties and other 

 properties of the solvent, such as its density, viscosity, and dielectric con- 

 stant. Additional light might also be thrown on the cause of the complete 

 divergence of the change in the ionization of largely ionized compounds 

 with the concentration from the requirements of the mass-action law* a 

 divergence which constitutes one of the most serious imperfections of the 

 theory of solutions, and which may well conceal a discovery of great 

 importance. 



The first and most difficult part of this research consisted in the con- 

 struction of a conductivity vessel composed internally of material unacted 

 upon by aqueous solutions and capable of withstanding without leakage 

 the high vapor-pressure of such solutions up to the critical temperature. 

 This portion of the work was carried out by Dr. W. D. Coolidge. After 

 three years' continuous work upon this problem, the mechanical difficulties 

 were overcome and a platinum-lined bomb with insulated electrodes was 

 constructed which remains perfectly tight at any rate up to 306, which 

 occasions only an unimportant contamination even in salt solutions as 

 dilute as -joVo normal, which yields conductivity measurements accurate 

 to 0.2 per cent, or less, and which at the same time makes possible specific- 

 volume determinations, which are essential to the interpretation of the 

 results. Now that a knowledge of the necessary mechanical devices has 

 been acquired, the making of such a bomb is an easy task for a skilled 

 instrument-maker. Therefore, in Part II of this publication will be first 

 described in full detail, with the help of working drawings, the apparatus 

 used in the first measurements, and especially the construction of the 

 bomb, in order to make it readily available for investigators who desire 

 to pursue researches of the same kind or those requiring similar apparatus 

 (such, for example, as a calorimetric bomb). This description, together 

 with the results with sodium and potassium chlorides referred to in the 

 next paragraph, was published in November, 1903, in the Proceedings of 

 the American Academy of Arts and Sciences.f It is reproduced here, in 



*For a brief general discussion of this matter, see Noyes, Congress of Arts and 

 Sciences, 4, 311-323 (1904) ; Science, 20, 577-587 (1904) ; reviewed in Z. phys. Chem., 

 52, 634-636 (1905). 



fProc. Am. Acad., 39, 161-219 (1903). Also in Z. phys. Chem., 46, 323-378, and 

 in somewhat abbreviated form in J. Am. Chem. Soc, 26, 134-170. 



