136 PHYSIOLOGY. 



electrical current enters or leaves the electrolyte are called electrodes : 

 the anode and cathode. The electrically charged particles, the aggre- 

 gation of which constitutes a molecule of the electrolyte, are called 

 the ions of the electrolyte. The ions which, under the influence of 

 the electrical current, migrate to the anode are anions; those which 

 wander to the cathode, cathions. Thus, for example, Nad is an elec- 

 trolyte; Na and Cl are its ions; Na is the cathion, Cl the anion; in 

 the electrolysis of an NaCl solution the cathion, Na, wanders to the 

 cathode, the anion to the anode. According to Clausius, the con- 

 stituents of a greater or less number of dissolved molecules exist in a 

 free state, and move in all directions through the solution even before 

 the passage of an electrical current. Only the presence of the free 

 ions makes it possible that such a solution can at all conduct e 1 ec- 

 tricity. If we dissolve crystals of sodium chloride in water, a part of 

 the NaCl molecules split into ions: N"a and Cl. If an electrical cur- 

 rent is passed through such a solution the ions, which at first were 

 moving in all directions, are arrested and drawn to the poles. An 

 ion is the electrolytic representative of an atom. 



In an aqueous solution of an acid, the kation is hydrogen, and the 

 anion is the acid radical. In the solution of a base, the kation is 

 the metal or metallic radical, as for example, ammonium NH 4 , and 

 the anion, the hydroxyl OH. In the solution of a salt, the kation is 

 the metal, and the anion the acid radical. The kations carry the 

 positive electricity, and therefore move towards the negative pole or 

 cathode. The anions carry the negative electricity, and therefore 

 move towards the anode. Suppose we have an aqueous solution of 

 hydrochloric acid ; the positive ion is hydrogen and the negative 

 chlorine, the water being supposed to play no part in the conductivity. 

 If a solution of sodium sulphate be electrolysed, the positive ion is 

 sodium, the negative S0 4 . It is convenient to have a system of 

 names for the ions derived from acids, bases, and salts, which shall 

 represent not so much the ions as the particles, but rather ionic sub- 

 stances. 



The following system has been proposed, in which the names are 

 derived directly from the names of the ionized salts. The positive 

 ions receive their names from the positive radicals of the salts, acids, 

 and bases by the replacement of the terminations, by the suffix ion; 

 for example : 



Hydrion, H' Sodion, NY 



Calcion, Ca' Argention, Ag' 



Ammonion, 



