Sosman — Platinum- Rhodium Thermoelement. 



11 



some value in indicating the course of the curve of e.m.f. and 

 composition. The data have been corrected to our tempera- 

 ture scale, and also for the difference in e.m.f. standards. 



Holborn and Day* in 1899 obtained the e.m.f. of pure plat- 

 inum against two samples of pure rhodium up to 1300°. The 

 data have been corrected to correspond to our temperature 

 scale. 



Waidner and Burgess f measured the e.m.f. of the 10 per 

 cent against the 20 per cent alloy, using two samples, at vari- 

 ous points up to 1755°. The addition of this value to the 

 e.m.f. of the 10 per cent alloy against pure platinum gives an 

 independent check on our direct measurements with the 20 

 per cent alloy. As appears on the curves in fig. 4, the agree- 

 ment is very good. 



Table III. — Thermal E.M.F. of Pure Platinum against 

 Rhodium Alloys, in Millivolts. 



Platinum- 





H 



5^ 



10,^ 



15^ 



20^ 



^m 



40^t 





t 







Stand- 

 ard 



100^ § 









Low 



High 













100° 



0-21 



0-55 



0-63 



0-64 



0-64 



0-65 









0-65 



200 



0-42 



1-18 



1-41 



1-43 



1-43 



1-50 















1-51 



300 



063 



1-85 



2-28 



2-32 



2-82 



2-41 





2-34 



3-45 



2-57 



400 



0-84 



2-53 



3-21 



3-26 



3-25 



8-45 



3-50 



8-50 



3-64 



8-76 



500 



1-05 



3-22 



4-17 



4-28 



4-23 



4-55 



4-60 



4-74 



4-93 



5-08 



600 



1-25 



3-93 



5-16 



5-24 



5-28 



5-71 



5-83 



6-06 



6-31 



6-55 



700 



1-45 



4-62 



6-19 



6-38 



6-37 



6-94 



7-18 



7-49 



7-80 



8-14 



800 



1-65 



5-38 



7-25 



7-35 



7-33 



8-28 



8-60 



9-01 



9-37 



9-87 



900 



1-85 



6-05 



8-35 



8-46 



8-43 



9-57 



10-09 



10-67 



11 09 



11-74 



1000 



2-05 



6-79 



9-47 



9-60 



9-57 



10-96 



11-65 



12-43 



]2-94 



18-74 



1100 



2-25 



7-53 



10-64 



10-77 



10-74 



12-40 



13-39 



14-33 



14-99 



15-87 



1300 



2-45 



8-29 



11-82 



11-97 



11-93 



13-87 



14-96 



16-39 



17-18 



18-10 



1300 



2-65 



9-06 



13-03 



1318 



13-13 



15-38 



16-65 



18-51 



19-51 



30-46 



1400 



2-86 



9-82 



14-33 



14-89 



14-34 



16-89 



18-39 



20-67 



21-73 





1500 



3-06 



10-56 



15-43 



15-61 



15-55 



18-41 



20-15 









1600 



3-26 



11-31 



16-68 



16-82 



16-75 



19-94 



21-90 













1700 



8-46 



12-05 



17-83 



1808 



17-95 



21-47 



23-65 











1755 



■3-56 



12-44 



18-49 



18-70 



18-61 



33-31 



34-55 











---- 



The summarized data are given in Table III. For the 10 

 per cent alloy three values are given : first, the lowest-reading 

 of the twelve elements used Avith the nitrogen thermometer; 

 second, the highest-reading; and third, the standard element E. 



The frequent comparisons of the platinum and rhodium 

 wires of the standard 10 per cent elements during the work 

 on the nitrogen thermometer, show that the differences among 



* Thermoelectricity in Certain Metals, this Journal (4), viii, 808-8, 1899 ; 

 Ann. Phys. (4), ii, 523, 1900; Sitzb. Berl. Akad., xxxvi, 691-5, 1899. 

 •f Bur. Bull. Standards, iii, 200, 1907. 

 X Holborn and Wien, 1892, loc. cit. 

 § Holborn and Day, mean value, 1899, loc. cit. 



