ELECTRICAL CONDUCTIVITY OF COTTON 



441 



This evidence is considered to indicate the close control of the 

 testing conditions made possible with the dynamic method, and 

 suggests that the decreases in area in the loops obtained by Sheppard 

 and Newsome may be due to small variations in thermostat tem- 

 perature about a mean value. On absorption this would have the 

 effect of giving too high a moisture content at equilibrium, due to 

 hysteresis; on desorption the equilibrium value would be too low. 



TABLE II 



Moisture Content and Insulation Resistance Data on Water-Boiled Cotton 



IN Equilibrium with Constant Atmospheric Humidities during 



Absorption and Desorption Cycles at 25° C. 



3012 Cotton — Sample A 



Equilibrium Relative 

 Humidity at 25° C. 



% 



Moisture Content 



% M.C. log % M.C. 



Insulation Resistance per 

 J-in. Length of 30/2- 

 ply Cotton Thread 



megohms log megohms 



First Cycle of Increasing Humidity — Absorption 



60.0 



75.0 



91.5 



Saturation (20 hours exposure) . 



2.21 X10« 

 6.3 XlO^ 

 8.93 XlO^ 

 9.35X10 



6.34 

 4.80 

 2.95 

 1.97 



First Cycle of Decreasing Humidity — Desorption 



91.5. 

 73.0. 

 60.0. 

 40.0 



3.80x102 

 9.75 XlO' 

 9.46X10* 

 2.77X10" 



2.58 

 3.99 

 4.98 

 6.44 



Samples dried 20 hours with drj^ air at 25° C. 



Second Cycle of Increasing Humidity — A bsorption 



40.0 

 60.0 

 73.0 

 91.5 



1.25 XlO^ 

 6.45X105 

 5.95 XlO* 

 1.00X103 



7.097 

 5.81 

 4.75 

 3.00 



hisiilntion Resistance-Relative Humidity Data 



Figs. 1 and 3 show hysteresis loops in the log I.R. — per cent R.H. 



curves, for both raw and water-boiled cotton. Hysteresis loops in 



this relation were shown in a previous paper - but no evidence was 



available to show the effect on the loop area of exposure of the 



- loc. cit. 



