228 



C. C. Hutckins — Thermo- Electric 



Materials and iweparation. 



The bismuth was prepared by Joseph Torrey of the Harvard 

 chemical laboratory. Mr. Torrey has made the preparation of 

 pure bismuth a special study with a view to the re-determination 

 of its atomic weight. It is freed from lead only with great 

 difficulty, and it is worthy of note that the samples used do not 

 show the lines of that impurity in the spark spectrum. 



The antimony employed was a portion of that prepared by 

 Professor Cook for his research upon its atomic weights. The 

 lead, which was made one element in all the junctions, was 

 prepared by electrolysis from the pure acetate. 



The metals are cast in thin laminae as follows. Two pieces 

 of plate glass are smoked slightly, or are very finely ground 

 and rubbed with plumbago. The metal being melted upon 

 charcoal or under fused sodium chloride, a little pool is poured 

 upon one plate and the other is applied to it as quickly as pos- 

 sible. In this way a leaf of very small thickness is obtained, 

 which can be cut into narrow strips with a straight-edge and 

 a thin graver. 



Results. 



The following table gives in column a the composition of 

 the alloy forming one element of the junction, the other ele- 

 ment being pure lead ; in t the mean temperature of the hot 

 and cold junctions; in t' the difference of temperature; in d 

 the galvanometer deflection per degree difference of tempera- 

 ture : in k the thermo-electric height relative to lead. The 

 signs in column h are in accordance with the convention that 

 for the Peltier effect a current running down generates heat. 



Bi 



Sb 











50 



50 



32-0 



18-5 



1-960 - 



- 1845 



60 



40 



31-0 



25-1 



3-127 



2944 



70 



30 



31-4 



24-2 



4-230 



3982 



80 



20 



31-0 



22-7 



5-710 



5374 



90 



10 



32-0 



21-5 



6-576 



6179 



95 



5 



31-2 



24-5 



7-205 



6782 



97-5 



2-5 



30-3 



22-5 



7-220 



6796 



98-75 



1-25 



29-6 



24-6 



5-558 



5232 



Commercial Bi 





30-6 



25-2 



4-323 



4069 



Pure Bi 





33-0 



26'0 



6-869 



6466 



