RESISTANCE AND ELECTROMOTIVE FORCE. 



29 



The silver-platinum line marked Ag + Pt, and the silver-gold 

 line, marked Ag + Au, are not straight. In particular, it is to 

 be noticed that a very small percentage of platinum added to pure 

 silver increases the resistance of the metal very greatly indeed. 



4 



Zn=3.68 



Ag-1.00 



x> 



PERCENTAGE -(-COMPOSITION 





Sn=8.35 



Au-1.28 



2O 4O 6O 



Fig. 12. 



In respect to electrical resistance, the alloys of tin, lead, cad- 

 mium and zinc are similar to the alloys of zinc and tin, that is to 

 say, the resistivity varies in proportion to the percentage of one 

 of the metals in the alloy. Alloys of most other metals are more 

 or less similar to the alloys of silver and gold and of silver and 

 platinum, and, in general, the addition of a very small percentage 

 of one metal to another increases the resistivity greatly. The 

 exact opposite to this is true of many non-metallic substances, a 



