MORSE AND SARGENT. — RESISTANCE OF LEAD ACCUMULATOR. 603 



with the rest of the set. Most of our measurements at this tempera- 

 ture were made at the beginning of the work, and it is quite possible 

 that some lag error has caused this slight variation. The values for re- 

 sistances at 8.5° were still harder to fix, but the curve given is the aver- 

 age of so many measurements that its correctness is fairly certain. At 

 the higher temperatures the lag becomes much less troublesome. The 

 explanation which suggests itself is that this slow change corresponds 



100 120 IHO 160 lao zoo 220 2H0 260 2b0 JOQ 

 TIME- MINUTES 



Figure 7. Resistance and voltage curves for a Plante cell during complete 

 discharge and reversal. 



to a chemical reaction. Probably lead sulphate is dissolved as the tem- 

 perature is raised and precipitated as it is lowered. This would be 

 just such a process as would result in the slow adjustment of the cell 

 resistance to a new temperature. 



This explanation is made more probable by some experiments we 

 have made in an ordinary conductivity vessel with platinum electrodes, 

 filled with sulphuric acid from our cell. Some pieces of lead and lead 

 peroxide from a partially discharged cell were placed in the vessel and 

 the conductivity followed after a change in temperature. The lag of 

 resistance behind temperature is just as noticeable in this arrangement 

 as in the more complicated cell under investigation, and there seems to 



