408 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



are not able to account for the properties of metallic substances at very 

 low temperatures. Neither are they able to account successfully for 

 the properties of alloys and of liquid metals. 33 



It is obvious that the electrical properties of metallic substances are 

 extremely sensitive to all agencies. Temperature and density, as well as 

 all external forces, have a marked influence upon the electrical properties 

 of metals, and particularly on the conductance. So, also, the properties 

 of metallic substances are very sensitive to change in the state of the 

 system. The formation of compounds, of mixed crystals, or any poly- 

 morphic change is invariably accompanied by a great change in electrical 

 properties. Ultimately, it would appear that a study of the electrical 

 properties of metals, and particularly of metallic compounds, should yield 

 some clue as to the constitution of these substances. At the present time, 

 however, the constitution of metallic substances, and particularly of 

 metallic compounds, remains an unsolved problem. 



18 Very complete references to the theories dealing with metallic conduction are given 

 by Koenigsberger, loc. cit., p. 385, above. 



