INORGANIC SOLVENTS. 5 



sulphur dioxide) , that the molecular conductivity at first increases with the 

 temperature, passes through a maximum, and then diminishes as the critical 

 temperature is approached. This is seen at once to be just what would be 

 expected from the polymerized solvent theory of Dutoit and Aston. As 

 the temperature rises the association of the solvent decreases, and this would 

 be expected to diminish the ionizing power. They have also determined the 

 molecular weights of a number of electrolytes (salts) in liquid sulphur dioxide, 

 by the boiling-point method; reaching the remarkable result that many of 

 these salts show a molecular weight greater than normal, or what is the same 

 thing, the value of the van't Hoff coefficient "i" is less than unity. This 

 they endeavor to show is due to the fact that, in addition to the electrolytic 

 dissociation, an association takes place in the solutions in sulphur dioxide. 

 Facts similar to the above were noticed by Franklin and Kraus * in their 

 work on liquid ammonia. 



The remaining work in inorganic solvents we owe chiefly to Walden. 2 

 He has investigated the solvent and ionizing power of the following com- 

 pounds : Phosphorus trichloride, phosphorus tribromide, phosphorus oxy- 

 chloride, arsenic trichloride, antimony trichloride, antimony pentachloride, 

 boron trichloride, silicon tetrachloride, tin tetrachloride, sulphur monochlo- 

 ride, sulphuryl chloride, thionyl chloride, sulphur trioxide, and liquid bro- 

 mine. Of these, sulphur monochloride, sulphuryl chloride, thionyl chloride, 

 phosphorus oxychloride, arsenic trichloride, and antimony trichloride show 

 considerable ionizing power, while solutions in the remaining solvents ex- 

 hibit only the very slightest conductivity. In his next paper Walden adds 

 a study of arsenic tribromide, chlorsulphuric acid, sulphuric acid, and the 

 dimethyl ester of sulphuric acid. All of these show a strong tendency to 

 ionize dissolved electrolytes. It is important to notice from this work of 

 Walden that there appears to be no connection between dissociating power 

 and chemical constitution. Antimony pentachloride does not dissociate 

 electrolytes, while the trichloride dissociates to a very considerable extent. 

 On the other hand, phosphorus trichloride does not dissociate, while phos- 

 phorus oxychloride does. It is thus evident that, among the inorganic sol- 

 vents at least, a knowledge of the dissociating power of one solvent tells 

 us nothing as to the dissociating power of substances closely related 

 chemically. 



Oddo 3 has also shown that phosphorus oxychloride strongly ionizes elec- 

 trolytes. Tolloczko, 4 as well as Garelli and Bassani, 5 have worked with the 

 halides of arsenic and antimony, showing them to have ionizing power. 



1 Amer. Chem. Journ., 20, 836 (1898); 24, 3 Atti R. Accad. dei Lincei Roma, [5] 10 



83 (1900). 452. 



1 Ztschr. anorg. Chem., 25, 209 (1900); 29, 4 Ztschr. phys. Chem., 30, 705 (1899). 



371 (1903). B Atti R. Accad. dei Lincei Roma, [5] 10 



255. 



