OP ARTS AND SCIENCES. 221 



XV. 



CONTRIBUTIONS FROM THE PHYSICAL LABORATORY OF 

 HARVARD UNIVERSITY. 



THE ELECTROMOTIVE FORCE OF ALLOYS. 

 By John Trowbridge and E. K. Stevens. 



Presented May 29th, 1883. 



The best study of alloys and the most thorough work on them has 

 been done by Matthiessen, who proved conclusively that alloys 

 were neither mechanical mixtures nor chemical compounds, but what 

 he terms, in a general way, " a solidified solution of one metal in 

 another." He also showed that, with reference to the formation of 

 alloys, metals were divided into two classes ; — the first class being 

 those which, when alloyed with each other, give a conductivity in pro- 

 portion to the respective volumes of the two metals ; and the second, 

 those which, when alloyed with each other, give a conductivity which 

 is less than that of the respective volumes of the two metals. 



The aim of this investigation has been to note the variation of 

 electromotive force in different alloys of the same metals, and to de- 

 duce, if possible, some general law which governs the variation. 



Two sets of alloys were used, — one set of lead and tin, and the 

 other of copper and zinc. The first set was made by taking the pro- 

 portional weights of lead and tin and melting them together in a cru- 

 cible, and then pouring them out on a flat surface and allowing them 

 to cool. The second set was made by melting a weighed amount of 

 copper in a Fletcher gas-furnace, and, when in a molten state, adding 

 more than the required amount of zinc, in order to make allowance 

 for volatilization. Pure metals were obtained, in order that the results 

 might be as accurate as possible. 



It was deemed sufficient, as far as the lead and tin alloys were con- 

 cerned, to weigh out carefully the required amounts of each metal, and 

 to take those weights as showing the composition. This could not be 

 done with the copper and zinc alloys, as it is impossible to determine 



