398 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



specific conductance of sodium amalgams passes through a minimum at 

 about 2.5 atom per cent of sodium. McCoy and West 15a have determined 

 the conductance of amalgams of substituted ammonium bases. The 

 conductance of these amalgams decreases with increasing concentration, 

 passing through a minimum. In general, liquid alloys whose components 

 do not form compounds exhibit conductance curves without pronounced 

 minima. On the other hand, alloys which form compounds often exhibit 

 pronounced minima. This is, for example, the case with alloys of sodium 

 and potassium. In the following table are given conductance values of 

 mixtures of sodium and potassium, together with their temperature coeffi- 

 cients. 18 



TABLE CLX. 



CONDUCTANCE OF LIQUID SODIUM-POTASSIUM ALLOYS AT 200. 



Specific 

 Atom Per Cent Conductance 



Potassium \i X 10~ 4 a X 10 3 



7.37 +3.85 



4.2 5.55 3.222 



8.0 4.42 2.43 



26.5 2.690 1.725 



44.5 2.150 1.555 



63.0 5.095 1.585 



82.0 2.250 1.860 



93.0 3.230 2.91 



100.0 4.59 4.98 



It will be observed that the conductance curve exhibits a minimum in 

 the neighborhood of 50 atomic per cent of sodium and potassium, which 

 corresponds with the composition of the compound NaK. The existence 

 of this compound has been established by means of the melting point 

 diagram. It will be observed, also, that the temperature coefficient of the 

 sodium-potassium alloys exhibits a minimum value at a composition cor- 

 responding with that of the compound. The conductance of alloys of 

 copper and lead exhibits neither a maximum nor a minimum, but the tem- 

 perature coefficient exhibits a minimum at a composition in the neighbor- 

 hood of 40 per cent of lead. The conductance curves of liquid alloys of 

 copper and antimony exhibit singularities corresponding with the com- 

 position of the compounds Cu 4 Sb and Cu 3 Sb. The temperature coeffi- 

 cients of both these compounds are negative, while, those of the pure 

 metals are positive. The conductance curve for liquid mixtures of copper 



McCoy and West, J. Phys. Chem. 16, 261 (1912), 

 16 Koenigsberger, \oc. cit, 



