LAWS OF ELECTROLYTIC DISSOCIATION 9 



tached from the positive atom. The first arrangement represents the 

 electrolytically dissociated portion, or the ions, while the second 

 represents the undissociated molecules (of NaCl). According to 

 the predominance of the first or second mode of atomic arrangement 

 stronger or weaker degrees of electrolj^tic dissociation are designated. 

 The condition of dissociation of an electrolyte is not a resting 

 state of equilibrimn; for one and the same molecule may in the 

 course of time pass back and forth between the dissociated and 

 undissociated state repeatedly. The "degree of dissociation" is a 

 static quantity only in the sense that it represents the ratio of the 

 dissociated portion to the total amount of electrolyte at a given 

 instant. Since even in the most dilute solutions the number of 

 individual molecules is enormous, the probability that a statistical 

 table composed of figures estimated at different times would yield 

 varying results is very slight. It is in this sense that in a solution 

 of an electrolyte a dynamic equilibrium exists, just as it does in 

 every solution in which an irreversible reaction has run its course to 

 a state of equilibrium. 



Radicals, such as OH, CN, etc., behave in the above respects 

 exactly as the ions of the individual elements do. 



Since the atom of hydrogen possesses but a single electron, it 

 follows that the hydrogen ion consists of a bare atomic nucleus 

 carrying a single positive charge. 



The theory of the hydrogen-atomic model admits of the possibil- 

 ity of the H-atom taking up a second electron and thus becoming 

 a negative ion. Indeed Moers^ (with Nernst) has recently demon- 

 strated that the definite crystalUne compound lithium hydride, LiH, 

 on electrolysis when in a molten state produces positive Li-ions and 

 negative H-ions; i.e., the hydrogen is evolved at the anode instead 

 of at the cathode, as is usual. Here it behaves as a halogen, just as 

 it is frequently simply substituted for a halogen in organic com- 

 pounds. Otherwise it behaves as a metal. In aqueous solution 

 negative H-ions cannot occur. 



3. The dissociation of water 



Water belongs to that group of substances which undergo electro- 

 lytic dissociation. The laws of electrolysis have been worked out 



' W. Nernst, Dtsch. Bunsen-Ges. 1920; K. Moers, Zeitschr. f. anorg. u. 

 allg. Chem. 113, 179 (1920). 



