MOESE AND SARGENT. — RESISTANCE OF LEAD ACCUMULATOR. G09 



interest because they show how dynamic a thing the momentary equilib- 

 rium in such a cell must be. A set of these derived curves is given in 

 Figure 1 1. The points on the curve T = are for open circuit and they 

 give the temperature-resistance curve of Figure 4. The points on the 

 curve T = 30 are resistances taken from the isothermal curves as they 

 are cut by a vertical line at 30 minutes of discharge, and so on for the 

 other curves. 



2.0 



IS 



1.6 



»^ /.y 



"J 



o 



1.2 



1.0 



03 



10° 



HO" 



50 



20° 30° 



TEtlPERAfURE 



Figure 12. Temperature effect on voltage after various periods of discharge 



The slope of the line T = gives the temperature-coefficient of 

 resistance at the temperature corresponding tp the point where the 

 slope is determined. The slope at any point on one of the other 

 curves is the temperature coefficient corresponding to the temperature 

 where the slope is taken, but for all the curves except T = the con- 

 dition of the cell is one of dynamic momentary equilibrium. The 

 slopes are nevertheless temperature coefficients corresponding to this 

 particular state in the cell and they are of great interest in disclosing 

 the condition of the cell. In fact it Avould be hard to find a more 

 striking expression of the complex system under observation than that 

 given by these curves. 



The change in temperature-effect is enormous. At T = the 

 coefficient is about 1.5% per degree C. At T = 150 minutes the 

 coefficient has reached 23% per degree C 



VOL. XLVI. — 39 



