322 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



current and in solution their conductance is low. Nevertheless, solutions 

 of non-polar substances may exhibit marked electrolytic properties. So, 

 for example, solutions of iodine bromide, iodine trichloride, iodine, phos- 

 phorus trichloride, phosphorus pentabromide, etc., conduct the current to 

 a measurable extent in sulphur dioxide, arsenic trichloride, sulfuryl chlo- 

 ride, nitrobenzene, 58 etc. So, also, for example, solutions of iodine in 

 bromine conduct the current. Walden has suggested that in these solu- 

 tions one electronegative atom functions as anion and another as cation. 

 For example, he assumes that a reaction of the type: 



I, = !* + !-, 



takes place when iodine is dissolved in sulphur dioxide. The investiga- 

 tions of Bruner and Galecki 59 and Bruner and Bekier 60 have shown that, 

 in sulphur dioxide and nitrobenzol, the halogens and their compounds 

 are not constituents of the positive ions. At any rate, on electrolyzing 

 such solutions, the negative element may be concentrated at the anode. 

 The nature of the cation in these solutions is uncertain, but there appears 

 to be little doubt that the electronegative constituent is associated with 

 the anion. Apparently, the electrolytic properties of these solutions are 

 due to the formation of a complex between the strongly electronegative 

 element or compound and the solvent, in which, presumably, the solvent 

 molecule, in part at least, functions as cation. 



So far as the electrolytic properties of their compounds are concerned, 

 strongly electronegative elements or groups of elements may not function 

 as cations, although it is possible that in certain cases they may be asso- 

 ciated with the cation in the form of a complex ion, as is the case, for 

 example, with iodine in the intermediate ion of cadmium iodide in 

 aqueous solution. On the other hand, as we have already seen, metals, 

 which normally are electropositively charged in their compounds with 

 more electronegative elements, may, under certain conditions, function as 

 anions. For example, sodium and lead in ammonia react to form a solu- 

 tion in which the two elements are present in the ratio of 2.25 atoms of 

 lead to one atom of sodium, when metallic lead is present in excess. 61 

 On electrolysis of these solutions, lead is precipitated on the anode. The 

 properties of these complex anions have already been discussed. 



68 Walden, Ztschr. f. phj/s. Chem. tf, 385 (1903). 



Bruner and Galecki, Ztschr. f. phya. Chem. 8$, 513 (1913). 



60 Bruner and Bekier, i&id.. 8}, 570 (1913). 



"Kraus, J. Am. Chem. Soc. 29, 1557 (1907) ; Smyth, iWd., 39, 1299 (1917), 





