278 



Table 310. 

 CONDUCTING POWER OF ALLOYS. 



This table shows the conducting power of alloys and the variation of the conducting power with temperature.* The 



,06 

 values of C^ were obtained from the original results by assuming silver = — ^ mhos. The conductivity is taken 



as Cj= C„ (i — at-^bfi), and the range of temperature was from o° to ioo° C. 



The table is arranged in three groups to show(i) that certain metals when melted together produce a solution 

 which has a conductivity equal to the mean of the conductivities of the components, (2) the behavior of those 

 metals alloyed with others, and (3) the behavior of the other metals alloyed together. 



It is pointed out that, with a few exceptions, the percentage variation between o*^ and 100^ can be calculated from the 



formula 7':=/'^ — ^ where/ is the observed and /' the calculated conducting power of the mixture at 100^ C, 

 and /', is the calculated mean variation of the metals mixed. 



Note. — Barus, in the " Am. Jour, of Sci." vol. 36, has pointed out that the temperature variation of platinum 

 alloys containing less than 10% of the other metal can be nearly expressed by an equation,)' = — — w, where ^ is the 



temperature coefficient and x the specific resistance, m and n being constants. If a. be the temperature coefficient at 

 0° C. and i the corresponding specific resistance, s (o -)-»/) = «. 



For platinum alloys Barus's experiments gave nf=- — .000194 and n = .0378. 



For steel m ^ — .000303 and « ^ .0620. 

 Matthiessen's experiments reduced by Barus gave for 



Gold alloys tnrrz — .000045, n = .00721. 



Silver ' mz=: — .000112, «== .00538. 



Copper " m=z — .000386, n =z .00055. 



* From the experiments of Matthiessen and Vogt, " Phil. Trans. R. S." v. 154. 

 t Hard-drawn. 



Smithsonian Tables. 



