66 



H. 8. Carhart — One- Volt Standard Cell. 





Table II. 





Difference of 



Total E. M. F. 





Temperature. 



in volts. 



E. M. F. per degree C. 



49°'0 



•02876 



•000587 



45-5 



•02662 



•000585 



42*9 



•02570 



•000579 



39-4 



•02295 



•000582 



34-8 



•02050 



•000589 



32-4 



•01913 



•000590 



28-9 



•01668 



•000577 



26-1 



•01499 



•000574 



22-5 



•01301 



•000578 



18-0 



•01040 



•000580 



12*6 



•00750 



•000595 



10'6 



•00612 



•000577 



8'4 



•00490 



•000583 





Mean, 



-f '000584 





Table III. 





Difference of 



Total E. M. F. 





Temperature. 



in volts. 



E. M. F. per degree 0. 



47°-8 



•03314 



•000693 



45*4 



•03146 



•000693 



42-8 



•02949 



•000689 



39-4 



•02706 



•000686 



37-1 



•02554 



•000688 



34-4 



•02340 



•000680 



32-1 



•02174 



•000677 



28-2 



•01928 



•000687 



25-6 



•01729 



•000675 



23-1 



•01561 



•000675 



20-1 



•01353 



•000673 



16-8 



•01125 



•000669 



13-2 



•00882 



•000668 



10-9 



•00730 



•000669 



7-4 



•00517 



•000698 





Mean, 



+ •000681 



Both of these thermal E. M. F.'s are positive. The tempera- 

 ture coefficient should therefore be 



0-000681 — 0-000584=:0-000097 as a mean. 

 This corresponds very closely indeed with the value found 

 by observation on a one-volt cell. It will be observed that it 

 is only necessary to take the difference of the above electro- 

 motive forces to obtain the temperature coefficient, since the 

 E. M. F. of the cell is one volt. The coefficient is positive 



because the value of — for the positive side of the cell is in 

 a jl 



excess of that for the negative side. 



