370 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



In dilute solutions, this effect is very pronounced and, in the immediate 

 neighborhood of the anode, the solvent appears to be completely freed 

 from the metal, since the solution becomes colorless and transparent. 

 No reaction of any kind appears to take place at the anode surface, no 

 gas is evolved, nor is any manner of deposit observable. On subjecting 

 a solution of sodium in ammonia contained in a U-shaped tube to ex- 

 tended electrolysis, the metal may be completely removed from the 

 anode limb and transferred to the immediate neighborhood of the 

 cathode surface. In this, no actual loss of the metal occurs, since on 

 reversing the current, or on mixing the solution by shaking, the original 

 solution is reproduced. Apparently, therefore, there is present in these 

 . solutions a negative carrier whose passage into the anode leaves behind 

 it no observable material effect. The nature of the phenomenon is not 

 appreciably altered if another metal is employed in place of sodium. 

 We commonly associate the characteristic metallic properties of a 

 substance with the atoms of this substance; and, in the case of com- 

 pounds, we associate metallic properties with the electropositive con- 

 stituent. A brief consideration, however, will serve to show that this 

 conception is erroneous, and that the electropositive constituent of a 

 compound is entirely nonmetallic in its character. The metals owe their 

 characteristic metallic properties, not to the electropositive constituent 

 present, but, rather, to a common electronegative constituent. If a solu- 

 tion of potassium in liquid ammonia, which has a characteristic color, 

 is placed between two solutions of potassium amide, which are trans- 

 parent, then, on passing a current through this system of solutions, the 

 motion of the color indicates the direction in which the free metal is 

 transported under the action of the current. If the characteristic prop- 

 erties of a solution of potassium in ammonia were due primarily to the 

 presence of an electropositive constituent, then we should expect that 

 the color would move toward the cathode. It has been found, however, 

 that, actually, under these conditions, the color moves toward the anode. 

 As has been shown, potassium in liquid ammonia solutions is associated 

 with the cation and moves toward the cathode. It follows that the 

 transfer of the free metal in the solution, placed between the two solu- 

 tions of potassium amide, is effected by means of the negative carrier. 

 In passing a current through a system of the type described above, there 

 is no indication that anything takes place as the positive ions pass from 

 the potassium solution into the solution of potassium amide, save that 

 the color boundary gradually moves in a direction opposite to that of 

 the positive current, that is, toward the anode. It is probable, there- 

 fore, that the positive ion in a solution of metallic potassium in liquid 



