394 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



whether" elementary or compound, causes a marked decrease in the con- 

 ductance of the resulting homogeneous alloy. The decrease due to the 

 addition of a given amount of the second constituent is the greater the 

 lower its concentration. If the conductance is represented graphically 

 as a function of the composition of the system, the resulting curve is 

 throughout convex toward the axis of concentration. The minimum 

 point in all cases lies in the neighborhood of a composition of 50-50. In 



o 



Au 



20 UO 60 SO 



Composition, volume per cent. 



700 



Ag 



FIG. 68. Representing the Conductance of Homogeneous Alloys of Ag and Au as a 



Function of Composition. 



Figure 68 is shown the conductance curve at ordinary temperatures for 

 homogeneous mixtures of silver and gold. As may be seen, the conduct- 

 ance of either component is greatly reduced on the addition of the second 

 constituent. The decrease in the conductance due to the addition of a 

 second component depends upon the nature of the substance added and is, 

 in general, the greater the less electropositive the added constituent. 

 Thus, the decrease in the conductance of iron due to the addition of 

 carbon or silicon is much greater than that due to the introduction of 



