Mr Laws, Experiments on the Thomson Effect, etc. 179 



Experiments on the Thomson Effect in Alloys of Bismuth and 

 Tin. By S. C. Laws, St John's College, '1851 Exhibition' 

 Scholar. 



[Read 4 May 1903.] 



The variation with composition of some of the electrical 

 properties of alloys of bismuth and tin have been investigated by 

 Rollmann* von Ettinghausen and Nernstf, HutchinsJ, Spada- 

 vecchia§, and more recently Schulze||, and many interesting 

 results obtained. The present paper contains the results of some 

 experiments on the Thomson effect or specific heat of electricity 

 in such alloys. 



The value of the Thomson effect in bismuth has already been 

 found by Batelli U, but for the sake of comparison experiments 

 were first made with pure bismuth and then with alloys containing 

 increasing amounts of tin. 



The bismuth used in the experiments was obtained as pure as 

 possible by procuring the pure oxide and reducing this in porcelain 

 crucibles with pure potassium cyanide. 



In this way bismuth containing no impurity other than 

 002 per cent, of iron was obtained. 



The tin used was supplied as pure precipitated metal. 



The specimens with which the experiments were made were 

 cast in the form of cylindrical rods about 35 cms. in length and 

 5 mm. in diameter. 



In the case of the alloys the moulds in which the rods were 

 cast consisted simply of glass tubes of the required length and 

 diameter ; these were heated to about 240° C. in a bath of oil, and 

 the molten metal, which had been previously kept liquid and well 

 stirred for some hours, poured in and allowed to slowly cool. 



* Pogg. Ann. 83, p. 78, 1851. 

 t Wied. Ann. xxxm. p. 474, 1888. 

 J Amer. Journ. of Science, xlviii. p. 226, 1894. 

 § Nuov. Cim. ix. p. 432, 1899. 

 || Ann. der Phys. ix. p. 555, 1902. 

 II Accad. delle Sci. di Torino, Atti, xxn. p. 548, 1887. 



