S89 



Tempernture coefficient of ronchiclivitij of heat. 



The c'liaiige of" tliermai coiKliictioii willi lem])ei'a(iire was noticed 

 by FoRHKs [Fliil. Trans, Hoy. See. Ediii. Vol. 33 (18H2), p. 133]. 

 Generally I here is a decrease of condnctivity with increase of teni- 

 peratnre and as a similar decrease takes place in the electric con- 

 dnctivity of metals, it was snpposed by Forbes that in general the 

 thermal condnctivities of metals like iheir electric, diminished with 

 rise of temperature. 



Wiedemann and Fkanz [Pogg. Ann. 89, (1H53), 497j appeared to 

 show that there is some connection between conducting power for 

 heat and for electricity. 



For the metals were found not only lo follow the same order for 

 the two conductivities, but in man\ cases the numbers bore nearly 

 the same ratio to each other. 



More recent work has contirmed this supposition. I'he following- 

 are some of the values for metals of the ratio of the thermal con- 

 ductivity and (he electrical conductivity or k'c at 18^ V. as deter- 

 mined b^ Jaegek and Diesselhorst [Phys. Tech. Reichsanstall Wiss. 

 Abh. 3, (1900)], together with the themperature coefficient of the ratio. 



The electron theory of conduction for heat and for electricity gives 

 an explanation of the connection between the two quantities. 



According lo that theory the ratio should be proportional lo the 

 absolute temperature i.e. should have a temp, coelf. 0.00367 and at 

 0' ('., its value should be (i.3 li)"°. The temperature coefficient 

 of heat conductivity has been determined by IjOrenz [Wied. Ann. 

 13, 422, 582 (1881)], Stewart [Proc. Roy. Soc. 53, 151 (J 893), 

 Lees (Phil. Trans. A. 183, 481 (1892)] etc." 



Bui the data of only a few elements are a\ailable, so il is im- 

 possible to obtain a cuive with the insuflicient data, which at present 



2(5 

 Proceedings Royal Acad. Amsterdam. Vol. XVlll, 



