August 4, 1911] 



SCIENCE 



139 



tendency to gain or lose one or more elec- 

 trons. The tendency to lose electrons is 

 greatest for the alkali metals and least for 

 the noble metals. According to this view, 

 for example, sodium and chlorine react 

 with great energy because of the great 

 tendency for each atom of free sodium to 

 lose an electron, on the one hand, and each 

 atom of free chlorine to take up an elec- 

 tron, on the other. The action consists, 

 therefore, in the transfer of an electron 

 from an atom of sodium to an atom of 

 chlorine. The components of a molecule 

 of solid salt are therefore not an atom each 

 of sodium and chlorine, but an ion of so- 

 dium combined with an ion of chlorine, if 

 by the term ion we now mean atom ± an 

 electron. 



The more or less complete "electrolytic 

 dissociation" or "ionization" which occurs 

 upon dissolving a salt in water is then due 

 to the marked lessening of the electric force 

 which holds together the ions of the solid 

 salt by reason of the very great dielectric 

 constant of water. 



The application of the electron theory 

 to the metallic state by Riecke, Drude, 

 Lorentz, Thomson and others has led to 

 results of the highest significance. Though 

 the details of the relations of the electrons 

 to the atoms are viewed somewhat differ- 

 ently by different physicists, it is however 

 agreed by those who are working in this 

 field that metals owe their most character- 

 istic metallic properties of a physical na- 

 ture to the mobile or free electrons which 

 they contain. The absence of metallic 

 properties in the solid non-metallic ele- 

 ments is, by this hypothesis, due to the sup- 

 posed tendency of the atoms of such ele- 

 ments to gain, not lose, electrons : for which 

 reason such a non-metallic solid will con- 

 tain very few free or mobile electrons. 



Thus, according to one view, electrons 

 ■which are perhaps as numerous as the 



atoms of the metal, move about freely 

 among the atoms, with which they are con- 

 sidered to be in kinetic equilibrium. Elec- 

 tric conductivity is then due to the drift of 

 these electrons under the influence of the 

 potential in the wire. Thermo-conduc- 

 tivity of metals is explained equally satis- 

 factorily by the electron hypothesis. The 

 calculated ratio of thermal to electrical 

 conductivity and also the temperature co- 

 efficient of the ratio are in good agreement 

 with the facts. Other metallic properties, 

 including opacity to light, reflecting and 

 radiating power, the Hall effect, the Thom- 

 son effect, the Peltier effect, etc., are 

 equally well accounted for. 



The most characteristic chemical prop- 

 erty of a metal is its ability to form the 

 positive ions of salts. Every true metal 

 has this property well developed. If we 

 electrolyze a solution of a salt, say silver 

 nitrate, the free positive ions of silver are 

 attracted and move toward the negative 

 electrode ; on coming in contact with which 

 each ion has forced into it an electron, 

 which converts it into an atom of silver. 

 The aggregate of such atoms deposited on 

 the cathode has metallic properties; owing 

 to the great tendency of each atom to give 

 up an electron. 



When we come next to consider the be- 

 havior upon electrolysis of a salt of a com- 

 pound basic radical, it is difficult to see 

 wherein its behavior should differ from 

 that of a salt of a metallic element. In this 

 case, as in the other, positive ions are 

 attracted to the cathode, and upon strik- 

 ing the latter can gain electrons. If then 

 the electron theory of the metallic state is 

 as fundamental as it seems to be, the aggre- 

 gate of such free "neutralized" radicals 

 should be a body having metallic proper- 

 ties; in other words, a "synthetic metal." 

 For such a hypothetical body would be 

 made up of radicals, which, analogous t( 



