THE ELECTRICAL CONDUCTIVITY OF INDIUM AND 



THALLIUM. 



Alpheus W. Smith. 



The behavior of the electrical conductivity of metals when 

 the metal passes from the solid to the liquid condition is of 

 increasing interest and importance in the formation of an 

 electron theory of metallic conduction. Except for the excellent 

 work of Northrup,* little systematic work has been done in this 

 field. It is the purpose of this short paper to give some results 

 obtained for indium and thallium. 



In order to make possible observations on the metal in the 

 liquid as well as in the solid condition, the metal to be studied 

 was introduced into a glass tube one end of which was closed. 

 Four platinum wires were sealed into this tube so that they 

 were at right angles to its axis. Two of these wires served as 

 potential and two as current electrodes in the ordinary Thomson 

 double bridge method of comparing low resistances. This 

 glass tube was about 3 mm. in internal diameter and the dis- 

 tance between the potential electrodes was about 2 cm. A 

 sufficient quantity of the metal was introduced to fill the tube 

 above the platinum electrode farthest from the closed end. 

 The air was exhausted from the tube and it was then sealed off 

 to prevent the oxidation of the metal on fusion. After fusion 

 the metal was allowed to cool slowly from the liquid to the 

 solid state. 



In order to secure the necessary temperatures for these 

 observations a cylindrical electrical furnace wound with 

 nichrome wire was used, except for room temperature and the 

 temperature of melting ice. The temperatures were determined 

 by means of a mercury in glass thermometer which was filled 

 with nitrogen. The observations on the resistances were made 

 in the usual way with a Thomson double bridge which was 

 obtained from Wolff. The standard low resistance was a coil 

 had a resistance of 0.001 ohm at 20 C. The indium and 

 thallium were obtained from Merck & Co. No chemical anal- 

 ysis was made of them and no attempt to further purify them. 



* Jour. Franklin Inst. 175, pp. 153-161 (1913). 



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