Relations of the Alloys of Platinum. 



435 



special ingredients of the alloy, and which depends only on 

 the resistance-position of this alloy in the class. I venture to 

 assert therefore that the arrangement of points is in accordance 

 with a definite underlying law, with reference to which excep- 

 tional data are to be interpreted. The law in question appears 

 to me particularly noteworthy as being among those which spe- 



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Figure ]. — Showing the relation between temperature-coefficient (a) and elec- 

 , trical resistance (s ), in case of platinum alloys. 



cially hold for the solid state. In his experiments on the con- 

 ductivity of solid mercury, C. L. Weber* found its resistance 

 to increase fourfold in virtue of fusion. Simultaneously with 

 this variation, the temperature-coefficient of solid mercury 

 (0 00455) falls to the relatively very low value (0-000927 be- 

 tween — 30° and +45°) which holds for the liquid metal. 

 Weber points out the close approximation of the temperature 

 coefficient of solid mercury to that of the other solid metals, 

 and infers even closer agreement at temperatures sufficiently 

 below the melting point of mercury. It is in a similar sense 

 that in §1 I referred the properties to be investigated in this 

 paper to a class of alloys characterized by high melting points. 



* C. L. Weber, Wied. Ann., xxv, p. 245, 1885. The large variation of resist- 

 ance at the* melting point, observed in case of mercury and other metals and 

 alloys (K, Na, etc.), suggests the striking adaptability of these substances for 

 experiments on the relation between melting point and pressure ; or in general 

 on the continuity of solid and liquid state! Change of resistance is here the 

 criterion of fusion. 



