HISTORICAL SKETCH. 3 



HISTORICAL SKETCH OF WORK IN NON-AQUEOUS SOLVENTS. 



In considering more in detail the results which have led to the above 

 generalizations, we shall consider the work done, first in inorganic solvents, 

 second in organic solvents, and third in mixed solvents. 



INORGANIC SOLVENTS. 



Water has always been regarded as the best dissociant, but recently another 

 solvent, liquid hydrocyanic acid, has been found to produce greater disso- 

 ciation. 



HYDROCYANIC ACID. 



Schlundt 1 has measured the dielectric constant of liquid hydrocyanic 

 acid, and found the very large value of 95 at 21, a value which exceeds 

 that of water, which is 80, at the same temperature. It was, therefore, 

 important, as bearing on the Nernst-Thomson theory of dissociation, that 

 measurements of the conductivity of solutions in this solvent be made. 

 This has been done by Centnerszwer, 2 with the result that not only do solu- 

 tions in hydrocyanic acid show greater conductivity, but the dissociation is 

 also greater than in water. The substances worked with were potassium 

 iodide and trimethylsulphonium iodide. Their conductivity at was 

 nearly the same as the conductivity of aqueous hydrochloric acid at 25. 



WATER. 



The dissociation of a great number of substances in aqueous solution has 

 been determined by a variety of methods, including the conductivity method 

 of Kohlrausch, 3 the freezing-point method of Jones, 4 Loomis, 5 and others, 

 and the solubility method of Nernst 6 and Noyes. 7 The result of this work 

 has been to show that for a strong acid or strong base, or a salt of a strong 

 acid and a strong base, at a dilution of about 1000 liters the dissociation is 

 practically complete. In most solvents, however, it is impossible to deter- 

 mine directly, by the conductivity method, the value of the molecular con- 

 ductivity for complete ionization, since the dilution at which this is reached 

 is so great as to preclude the application of the conductivity method. The 

 best that we can do in these cases is to compare the values of /i c , at varying 

 dilutions, with the corresponding values of /* in aqueous solution. In 

 this way an approximation to the dissociating power of various solvents can 

 be obtained. 



1 Journ. Phys. Chem., 5, 157 (1901). 6 Wied. Ann., 61, 500 (1894); 67, 495, 591 

 'Ztschr. phys. Chem., 39, 217 (1902). (1896); 60,523(1897). 



3 Wied. Ann., 26, 160 (1885). 6 Ztschr. phys. Chem., 4, 372 (1889). 



4 Ztschr. phys. Chem., 11, 110,529; 12,623 7 Ibid., 6,241 (1890); 9,603(1892); 12,162 

 (1893). (1893); 16, 125 (1895). 



